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- Fabrication, Design, and Instrumentation
- Information Acquisition, Processing, and Display
- Optical Interaction Science
- Photonics and Opto-Electronics
- Theoretical Optics
- Optical Engineering
- Biomedical Optics
- Vision and Colour
- Nanotechnology and Optics
- Applied Optics to Artwork
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- Optical Engineering Post Deadline Paper
Fabrication, Design, and Instrumentation
Methodology for the third order astigmatism compensation in off-axis spherical reflective systems
Show abstract
The main constraint of classical off-axis reflecting systems is the primary astigmatism that by long time has been a
research topic of interest. This astigmatism in off-axis spherical reflective imaging systems can be eliminated by one
proper configuration. These configurations could be derived from the marginal ray fan equation and they are valid for
small angles of incidence. The conditions for the astigmatism compensation in configurations with two and three offaxis
mirrors have been derived and analyzed, which has not been reported previously. The expression that defines the
conditions for primary astigmatism compensation in a four-mirror system is presented. This shows that the marginal
ray fan equation can be used to obtain the condition for astigmatism compensation of a reflective system with any
number of mirrors.
Diffraction efficiencies profile by thickness and spatial frequency variation
Show abstract
The holographic gratings on photopolymer films are studied by different spatial frequency and thickness to determine the
evolution of diffraction efficiency during holographic recording. The experimental results are presented like a function of
energy exposure, thickness and spatial frequency. The photopolymer emulsion is prepared with potassium dichromate
and nickel (II) chloride hexahydrate in polyvinyl alcohol matrix. The maximum diffraction efficiency reached is at
spatial frequency (f2) for sample A.
Design and construction of the automated scatterometer for particle sizing
Y. Pérez-Moret,
Javier A. Martínez,
M. P. Hernández,
et al.
Show abstract
A design of a scatterometer is described for applications of Mie theory. The instrument comprises a goniometer,
a lock-in amplifier, a laser, and a photomultiplier tube (PMT). An embedded control programmable hardware
and Windows-based Virtual Instruments simplify the design of automation of the scatterometer. The software
has been modularly designed to provide independent control of the stepper motor for the motion of goniometer
arm, running and on-line displaying of angular scans, auto storage of the angular scan data. The obtained
benefits include facilitation of advanced data-collection techniques and collection of higher quality data. Quasimonodisperse
particle of the latex have been characterized with this set up. The measured size particles are close
to the reported nominal values. This result indicated that the experimental setup warrants adequate quality
measurement, which allows a reasonable solution to inverse problem.
Laser ablated glass microlens arrays: aberrations dependence on reflowing temperature
Show abstract
The Laser-direct writing technique combined with a reflowing thermal treatment has demonstrated its capability to
provide microlens array with small diameter and good focusing capabilities. In this paper we analyze the influence of the
thermal treatment at temperatures of 650°C, 660°C, and 670°C, on the optical aberrations of the manufactured glass
microlens arrays by ablation with a Nd:YVO4 laser. We observed that by increasing the reflowing temperature we reduce
the microlenses optical aberrations and increase the resemblance between microlenses. In particular at 670°C we obtain
high quality microlens arrays characterized with a root mean square aberration of λ/28 ± λ/77, strehl ratio of 0.9475±0.0352 and depth of focus of 16.438± 5.762 μm. Our results show the reliability of the combination of the Laser-direct
writing technique with thermal treatment for fabricating high quality microlens arrays.
Vector wave holographic optical mass storage
Show abstract
An optical recording technique, called retardagraphy, can record a retardance pattern of a birefringent object on a polarization-sensitive medium made of azobenzene copolymer. In holography, a recording laser beam must be split into signal and reference parts. In contrast, it is not necessary for the retardagrapy to split the recording laser beam. This feature simplifies the optical system. The multi-valued phase pattern recorded on the polarization-sensitive medium can be reconstructed by measuring a retardation between two polarization components. The optical recording and reconstructing methods of binary and multi-valued phase patterns are demonstrated by retardagraphy.
The effect of alignment errors in polarimetry of light using liquid-crystal variable retarders
J. M. López-Téllez,
N. C. Bruce
Show abstract
Experimental results using Liquid-Crystal Variable Retarders (LCVRs) to measure the four Stokes parameters of a light
beam simultaneously are presented. We use known waveplates (half-wave and quarter-wave) as known sources to
provide controlled polarization states to the Stokes polarimeter, and we use the measured Stokes parameters as functions
of the orientation of the axes of the waveplates as an indication of the quality of the polarimeter. The effects of errors in
optical alignment and nonlinearity of the retardance variation on the results are presented and discussed. We also present
results of simulations for comparison. Finally, we present the advances obtained in the development of a Mueller matrix
polarimeter for use in a goniometric scatterometer.
Measuring radii of curvature using a calibrated lateral shearing interferometer
Show abstract
A technique for measuring the radius of curvature of a convex optical surface is described. Its functioning
is based on a lateral shearing interferometer and the observation of the collimation of a laser beam. Two
interference patterns of straight fringes are obtained, and only when the fringes are parallel is the
measurement considered. Since a previous calibration with a laser tracker or similar device is required it
is not possible to measure surfaces with radii of curvature longer than ten meters due to dimensions of the
laboratory. Details of resolution and measurement uncertainty between calibrated and noncalibrated
modes of the instrument are presented.
Calculation of higher order dispersion coefficients in photonic crystal fibers
Show abstract
We present the calculations of the higher order dispersion coefficients in a photonic crystal fiber. The dispersion
coefficient is obtained from the calculated effective index of the fiber structure by double differentiation with respect to
the wavelength (or frequency), or from the integral formula used to calculate the group index. Although both approaches
are equivalent we show that they lead to totally dissimilar results, like different zero dispersion wavelength and hence the
higher-order dispersion coefficients are different. In fact, the way in which the higher-order dispersion coefficients are
calculated will affect the prediction of the dynamics of the supercontinuum generation. This effect will be discussed in
this work.
Measurement of absolute optical thickness by wavelength tuning interferometer
Show abstract
Absolute optical thickness is a fundamental parameter for the design of optical elements. In semiconductor industry,
it is necessary to measure the absolute optical thickness of the central part of the projection lenses with a high
accuracy. However, even when the geometrical thickness is perfectly known, a typical refractive index of fused-silica
has an ambiguity of 6 × 10-5 that gives an uncertainty of 180 nm in the optical thickness for a 3 mm-thick plate.
Moreover, the optical thickness measured by white light interferometry and wavelength tuning interferometry is an
optical thickness with respect to not the ordinary refractive index but the group refractive index. We measured the
ordinary optical thickness of a fused silica plate of 6-inch square and 3 mm thickness by a wavelength tuning
interferometer with a tunable phase shifting technique. We assumed the typical refractive index and dispersion of
the fused silica as approximate values. The absolute interference order for the optical thickness was finally
estimated, which gives a measurement resolution of typically 10 nm for the optical thickness.
Stokes polarimetry using liquid-crystal variable retarders and nonlinear voltage-retardance function
C. A. Velázquez Olivera,
J. M. López Téllez,
N. C. Bruce
Show abstract
Stokes polarimetry using variable retardance elements such as Pockel´s cells and liquid crystals is a well-developed
technique. There are two standard methods of analysis to extract the Stokes vector from the data using only one detector.
One is to use only certain values of the retardances to obtain data for a number of fixed polarization combinations. The
other is to use all the polarization combinations of the retardances for an oscillating voltage applied to the cells, and
perform a Fourier analysis on the time varying signal. This method requires a linear relationship between the applied
voltage and the obtained retardance. However, in general, for liquid-crystal variable retarders, this relationship is not
linear. We present an analysis of a proposed method to use a nonlinear voltage-retardance relation to extract the Stokes
parameters of a light beam. The method assumes a known nonlinear function relating the voltage and the retardance and
uses a least-squares fit of the measured data to the calculated Mueller matrix of the polarimeter.
PVA with nopal dye as holographic recording material
Show abstract
Cactus nopal dye is introduced into a polyvinyl alcohol matrix achieving a like brown appearance thick film, such that
they can be used as a recording medium. This dye material provides excellent property as photosensitizer, i.e., easy
handling, low cost and can be used in real time holographic recording applications.
The experimental results show the diffraction efficiencies obtained by recording grating patterns induced by a
He-Cd laser (442nm). For the samples, a thick film of polyvinyl alcohol and dye from cactus nopal was deposited by the
gravity technique on a glass substrate. This mixture dries to form a photosensitive emulsion.
High resolution confocal polarimeter for the living human retina
Show abstract
There is strong evidence that the living human retina has polarization signatures that could be linked to the presence of
Glaucoma, an ocular disease that is the second cause of blindness in the western world.
In a polarization sensitive ophthalmoscope, the amount of light that can be used is limited for the safety of the subject,
and the return is typically a small fraction of the light used for illumination, of the order of 10-6. Furthermore, the
acquisition rates have to be sufficiently fast to avoid eye-movement artifacts. The light-budget available to produce a
polarization image with a scanning laser ophthalmoscope is typically in the order of 10 nW, and pixel acquisition
sampling rates are of several MHz.
We are currently developing an imaging instrument for vision research and clinical vision applications and aim to
introduce it to the medical and clinical environment using objective methods of image quality assessment. Here we
discuss the stringent imaging requirements, polarimeter design, and show high resolution polarization retinal images.
Non-perpendicular incidence in transmissive LCSLM: influence in the modulation prediction
Show abstract
In general, to determinate applications of liquid crystal spatial light modulators (LCSLM), it is necessary to find the
display operational modulation curves, considering the optical setup in which it will be used. This requires the use of a
SLM physical model to characterize the Jones matrix of the device. From these, the modulator operation curve is
obtained under any polarization configuration, and it is possible to predict the SLM behavior, to modulate in amplitude
or phase modulation. The characterization procedure is usually performed with normal incidence. Nevertheless, if the
illumination is off-axis, it could deteriorate the prediction of their behavior and consequently the expected modulation of
polarized light. In this work we analyze experimentally the behavior of the transmissive LCDSLM when the incident
beam impinging on it is off-axis. It is observed that the amplitude modulation is scarcely noticeable, when the incident
light beam is non-perpendicular to LCD, different to configuration 0°, as it was characterized. The situation is different
when we study the phase only modulation configuration. In this case, a variation in operation curve versus inclination of
incident light beam is observed. This result can be important to optimize some experiments or to take advantage, in only
one optical setup, to implement polarized beams with controlled slight phase differences between them. Likewise, the
Jones matrix of the LCSLM dispositive is obtained, and it is possible to observe variations in any matrix components
whereas the angle of the incident light beam is varying. Also, experimental curves for amplitude and phase modulations
are presented.
Holographic approach to 3D television
Show abstract
The paper gives an overview on 3D television which can be realized by a number of methods: stereoscopy, autostereoscopy,
integral imaging, volumetric display, and digital holography where digital holograms - recorded
or computed - are fed to spatial light modulators (SLM). All methods have their specific advantages and disadvantages,
which can be reduced parallax, lacking motion parallax, limited lateral resolution, occlusion problem,
or the severe accomodation conflict, causing eye fatigue and other discomforts. By principle holography exhibits
none of these imperfections, but the problem of the necessary high space-bandwidth-product is the main obstacle
for its introduction for 3D TV up to now. The needed high space-bandwidth-product requires CCDs and SLMs
with higher number of pixels, a shorter pixel pitch, and faster computers than available today. Here we present
first solutions to the space-bandwidth-product problem, e. g. by restricting on horizontal parallax only, by
using eye-trackers resulting in calculation of only the observed small parts of the hologram, by employing image
plane holography instead of Fresnel- or Fraunhofer-holography, or by using a proper combination of electrically
together with optically addressable SLMs.
Holographic gratings implemented in a photopolymerizable glass: application to femtosecond laser pulses shaping
Show abstract
We present the capability of the holographic gratings implemented in photopolymerizable glasses to be applied in spatial
and spectral manipulation of femtosecond laser pulses. For this purpose we used volume phase holographic gratings
recorded by the interference of two monochromatic and coherent beams coming from a Nd-YAG continuous laser.
We carried out experiments to determine the main features of the diffracted beams originated by the interaction of
volume holographic phase grating structures with femtosecond pulses arising from the fundamental emission of an
amplified Ti: sapphire laser system and its second harmonic. Meanwhile we have performed experiments to determine
its damage threshold indicating that this material is an excellent candidate for intense-fields and ultrashort laser pulse
applications.
Dynamic moiré patterns and Michelson fringe patterns for profilometry: a results comparative analysis
Show abstract
In the present work we present a simple comparative analysis of the results in the optical Fourier transform profilometry
which fringe projection is produced by two different methods, dynamic moiré-like patterns and Michelson
interferometer. First, the Fourier transform profilometry technique is applied in the projected moiré fringe pattern onto an
object surface. Then, this result is compared to the Michelson fringe pattern projection in the same method of
profilometry that is applied using the same test object. We have conclude that dynamic moiré-like fringe patterns could
be used with some advantages, comparatively to the results obtained by the classical Michelson fringe patterns.
Optical properties and their variations at Co-Ni-B amorphous metallic alloys
Show abstract
It is well known that optical phenomena in metals at IR spectral region are connected with intraband optical
transitions and they are analogues of direct electrical conductivity (resistance) at low frequencies. It can be suggested
that in case of alternating current flux through an amorphous metallic ribbon in external magnetic field, correlation
between optical and magneto-transport properties can be emerged. It must be important that the objects of the
investigations are magneto-optical effects linked with diagonal components of the optical tensor unlike Kerr or Faraday
effects. Experimental appearance of magneto-optical effects comprises significant changes of optical conductivity and
real part of dielectric permeability via influence of external magnetic field. The magneto-transport properties depend on
the effective differential permeability, on the type of domain structure and corresponding densities of electron states at
the Fermi level.
Optical functions of the amorphous metallic alloys ribbons of Co-Ni-B are obtained at spectral region of 1.0-5.0 eV.
Changes of optical conductivity spectra of the ribbons' surface in the presence of applied external magnetic field are
revealed. Variations of optical and magneto-transport properties caused by superseding of one 3d transition metal (Co) to
another (Ni) are obtained. Parameters of electronic subsystem were calculated. Interconnection between electronic
structure of the amorphous metallic ribbons' surface and its magneto-transport properties is established.
Developing the refractive light beam shapers as lossless apodization systems suppressing the side-lobes in Fourier transform optical systems
Show abstract
The Fourier transform optical systems, creating an image and/or realizing its accurate spectral characterization, suffer
from appearing remarkable level of side-lobes in the image intensity distribution that reduce performances, in particular,
the dynamic range of these systems. Therefore, suppressing side-lobes in the image plane represents an actual practical
task being important for various scientific and technical applications such as, for example, direct imaging and spectral
characterization of Earth-like extra-solar planets or spectrum analysis of ultra-high frequency radio-wave signals with
exploiting an advanced acousto-optical technique. We suggest applying as apodization systems novel refractive optical
beam shapers of the field mapping type, which are able to convert the input (more or less) uniform intensity distribution,
peculiar to the majority of usually exploited sources of light, to arbitrary pre-scripted intensity distributions. In the case
of choosing, for instance, Gaussian, cosine on a pedestal, etc. distributions, these shapers make it possible to minimize
the total level of side-lobes significantly and to increase, in doing so, the dynamic range of optical data processing up to
40 dB or more. The operation principle of these beam shapers is based on inducing, in a control manner, spherical
aberration in order to provide the required intensity profile transformation and further compensation of that aberration.
As a result, the beam shapers operate as telescopes of special type; they produce a low divergence collimated beam with
a target intensity distribution and flat wave front. We describe the beam shaper design, implementation examples, and
results of practical applications to the acousto-optical technique of precise multi-channel spectrum analysis.
Simultaneous phase shifting interferometry based in a Mach Zehnder interferometer for measurement of transparent samples
Show abstract
A Mach Zehnder (MZ) interferometer was implemented to analyze a phase object using polarization phase-shifting
interferometry. The Mach Zehnder interferometer produces two beams with circular polarization of opposite rotations
one respect to the other. The system is coupled to a 4-f system with phase grating in the Fourier plane, interference of the
fields associated with replicated beams centered on the diffraction orders is achieved by a proper choice of the beams
spacing with respect to the gratings period. The optical configuration allows obtaining n-interferograms in one shot. The
configuration presented does not require micro-polarizer arrays or additional software to eliminate noise caused by
vibration, as the system is stable itself and uses conventional polarizing filters. Considering the object under study a thin
phase object, experimental results are presented.
Parallel phase shifting interferometry using a double cyclic shear interferometer
Show abstract
In this work we present a parallel polarizing phase shifting interferometer based in a Double Cyclic Interferometer
(DCSI) to analyze transparent samples. This system has the advantage of generating four beams that can interfere
properly; this can reduce the number of captures needed in phase shifting interferometry. The interferometric system
generates two π-shifted interferograms, which are recorded by the CCD camera in a single-shot. For the processing of
the optical phase data map, a parallel phase shift can be generated by placing a linear polarizer covering two patterns.
We analyze the cases of four patterns with arbitrary shifts captured in two shots. The unwrapped phase is processed by
Kreis methods. Experimental results obtained by the proposed interferometer are presented.
Slope measurement of a phase object
Show abstract
An interferometric method to measure the slope of phase objects is presented. The analysis was performed by
implementing of a polarizing phase shifting cyclic shear interferometer coupled to a grating interferometer. This system
can obtain four interference patterns with adjustable phase shifts and variable lateral shear. In order to extract the slope
of a phase object, is analyzed the optical phase applying the classical method of phase extraction.
Characterization of planar waveguides fabricated by multiple sol-gel dip-coatings
Show abstract
Planar step-index waveguides of SiO2:TiO2 and ZrO2:CeO2 in multilayer structures were prepared onto commercial glass
substrates using a sol-gel technique combined with dip-coating. These coatings were previously optically characterized
by Ellipsometry. These glassy coatings were structural characterized by Transmission Electron Microscopy (TEM),
Energy Dispersive X-ray analysis and Confocal Microscopy. Thicknesses of 1050 nm and 500 nm and refractive indices
of 1.64 and 2.07 for SiO2:TiO2 (70:30) and ZrO2:CeO2 (70:30) waveguides were obtained, respectively, by the analysis
of the guided TE and TM modes observed by Dark m-line Spectroscopy. Losses of 1.32 dB/cm and 0.86 dB/cm were
respectively measured by a method based on scattered light.
Variable magnification in numerical reconstruction of digitally recorded holograms
Show abstract
The numerical reconstruction of digitally recorded holograms can be done via different approaches. Convolution,
angular spectrum and Fresnel transform are the most widely used. The size of the reconstruction pixel equals that of the
recording device for the two former and for the latter that size is controlled by the experimental parameters; wavelength,
number of pixels and reconstruction distance determine the achievable size of the of the reconstructed pitch hence the
magnification of the holographic system. It has been a challenge to have a numerical reconstruction method in which the
magnification can be chosen at will. In this work, a method for numerical reconstruction of digitally recorded holograms
with variable magnification is presented. It is supported on the Fresnel-Bluestein transform that allows for changing the
magnification, namely the size of the reconstruction pixel, independent of distances, wavelength and number of pixels.
The method is applied to reconstruct holograms recorded in off-axis and in-line setups. The reached magnification is
contrasted with that achieved as the holograms are reconstructed with Fresnel transform. Since the proposed method
does not modify the number of pixels of the hologram, neither the wavelength nor the reconstruction distance, it suits for
application like color digital holography, metrological application among others.
Microlenses fabrication on glass by combining laser with thermal-reflow technique
Show abstract
We describe a hybrid technique for fabricating microlens arrays on soda-lime glass substrates composed by a direct-laser
write and post thermal treatment. In particular we use a nanosecond Q-Switch Nd: YVO4 laser and a mufla Heraeus
furnace. Temperature dependence of the reflowing process was analyzed in the range of 620°C-670°C. An improvement
in the optical quality of the microlens arrays were obtained as temperature increases. The best microlens array was
obtained at 670°C with the following characteristics: diameter 47.89±6.65μm; focal length 510±10μm; and focal spot
size 2.82±0.02μm. The presented technique has been shown to be capable of fabricating low cost microlens arrays with
good optical quality.
Effective parameters of composed polarization systems
Show abstract
Here we present the results of theoretical and experimental determination of effective circular phase anisotropy, effective
linear phase anisotropy, effective linear amplitude anisotropy and effective circular amplitude anisotropy of a composed
polarization system with the properties of a quarter wave plate. It has been shown that the effective linear phase shift of
such polarization system is not equal to the quarter wave plate phase shift and depends on the single wave plate
parameters.
Polarimetry-based far-field method for high-resolution optical microscopy
Show abstract
We present a polarimetry-based far-field method for high-resolution optical microscopy. The method is based on the
measurement of scattering-angle-resolved polarization state distributions across the exit pupil of a high numerical
aperture objective lens and allows us to distinguish between different sub-resolution objects with no need for an active
scanning. Our numerical and experimental results show that the scattering-angle-resolved polarization state distributions
can be used in the characterization of particles and structures with features below or at the edge of the Rayleigh
resolution limit.
Optical systems and algorithms for phase-space tomography of one- and two-dimensional beams
Show abstract
The application of partially coherent optical beams for imaging, free space communication, random medium analysis requires controlling its mutual intensity. This task can be done using the phase-space tomography method consisting on the reconstruction of the Wigner distribution (WD), and therefore the mutual intensity, from its projections associated with the fractional power spectra. We propose two schemes that apply spatial light modulators (SLMs) for the measurements of the required WD projections in the case of one- and two-dimensional optical signals. The use of the SLMs allows rapid data acquisition and operative change of the projection number. Moreover, the measured intensity distributions do not require further rescaling, which accelerates the WD reconstruction algorithm and improves its efficiency. The developed numerical methods provide different ways for data analysis such as the reconstruction of the WD using the inverse Radon transform and its visualization for the case of one-dimensional signals; the determination of the mutual intensity for two fixed points without previous reconstruction of the entire WD for two-dimensional signals, etc. The validity of the proposed approaches has been verified experimentally for the test signals and the results are in a good agreement with the numerical simulations.
Generation of irradiance patterns using a semi-spherical meter of two degrees of freedom
Show abstract
The meter device presented in this work consists of a photo-detector mounted on the mechanism of a mobile rectangular
arc. One stepper motor located on the lateral axis of the device displaces the sensor along a semi-circular trajectory of
170°, almost half meridians. Another motor located at the base of the device enables 360° rotation of the illumination
source under test. This arrangement effectively produces a semi-spherical volume for the sensor to move within. The
number of measurement points is determined by programming the two stepper motors. Also, the use of a single photo-sensor
ensures uniformity in the measurements.
The mechanical structure provides enough rigidity for supporting the accuracy required by the data acquisition circuitry
based on a DSPIC. Measurement of illumination sources of different sizes is possible by using adjustable lengths of the
mobile base and the ring for a maximum lamp length of 0.16 m. Because this work is partially supported by a private
entity interested in the characterization of its products, especial attention has been given to the luminaries based on LED
technology with divergent beams. The received power by the detector is useful to obtain the irradiance profile of the
lighting source under test. The meter device presented herein is a low-cost prototype designed and fabricated using
recyclable materials only such as "electronic waste".
Application of Fraunhofer diffraction patterns for calculation of fractal dimension
Show abstract
In this paper the modificated method of calculation of fractal dimension is described. The method is based on effective
averaging procedure and deals with the number of fractal generation levels. The existing methods of calculation of
fractal dimension need the information about structure factor or scaling factor, which are generally unknown for real
objects.
The offered algorithm of calculation fractal dimensions allows to calculate fractal dimension of object with a relative
error less than 1%. Thus for calculation of dimension there is no necessity to reveal the factor of structure and scaling
factor. The method was checked on the wide range of two-dimensional fractals with exact self-similarity and different
values of fractal dimension.
Characterization of halogen lamps as secondary standard of luminous flux
Show abstract
This work presents a study of lamps characterization concerning its lamp output, current and voltage drift during
seasoning and regarding the use of theses lamps as luminous flux secondary standard. The 200W halogen lamps are
seasoned for 30 hours and during the seasoning period the relative drift of the lamp illuminance, current and voltage are
measured at each 3 minutes. The illuminance is measured using a photometer with detector head, the lamp voltage is
measured using a 6.5 digits voltmeter and the current is measured using a 6.5 digits voltmeter and 0.1 Ohms standard
resistor. The lamp current is controlled by a calibrated current power source with stability better than 1 mA. To reduce
the stray light, baffles are positioned between the lamp and the detector head. The alignment of experimental assembly is
made by a He-Ne Laser. Data of illuminance, current and voltage is acquired by software built in Labview database.
Among the 5 lamps seasoned, the best result presents the variation of illuminance of 0.04% per hour. This lamp is
chosen to become the secondary standard and its luminous flux is measured using an Ulbricht integrating sphere. This
method allows the laboratory to create secondary standard of luminous flux for its routine test and measurements and to
supply theses standards for Brazilian industry.
A system for the study of the photoacoustic phenomena in alloy samples of Fe2Mo
Show abstract
In this work, we present the design of a photoacoustic system to study the photoacoustic phenomena that can be used for
the experimental determination of the thermal diffusivity of solids. The photoacoustic system with an open
photoacoustic cell studies the photoacoustic signal of Fe2Mo pellets that have been produced from powder by gas-solid
reduction. we use the Rosencwaig and Gersho (RG) model to determine the thermal diffusivity of Fe2 Mo. The thermal
diffusivity of the Fe2Mo calculated is 0.0147 cm2/s ± 0.0001.
Assessment of residual stress on thin films by laser microtopography
Show abstract
Residual stress of as-deposited coatings may cause bending of the coating/substrate system. If residual stresses are
present and the overall deflection is small compared with the substrate thickness, then by symmetry the coated substrate
will take up a spherical curvature in the region away from the edges. Near the edges a complex stress state will be
present. However away from the edges this reverts to a simple stress state where stresses normal to the substrate and
shear stresses are zero The three-dimensional inspection of thin films deposited in thin substrates allows the assessment
of film's residual stress. In this communication we report on the use of this method illustrating it by performing the
residual stress evaluation PVD onto glass deposited thin films using optical non-destructive and non-invasive
microtopographic inspection using an active optical triangulation sensor developed by the first author at the Universidade
do Minho. It allows depth measures with resolutions down to 2nm and lateral resolutions down to 1μm. The three
dimensional map and corresponding coordinate set obtained allow the calculation of the stress distribution over the film.
Characterization of the optical sub-system in an advanced prototype of a new acousto-optical spectrometer for the Mexican Large Millimeter Telescope
Show abstract
A few optically matched by each other sub-systems related to an advanced prototype of acousto-optical spectrometer
for radio-astronomy are analyzed jointly. Rather precise control over the incident light polarization should be assured
in the scheme together with a required expanding of the incident light beam. Moreover, the needed light-beam
apodization, suppressing side lobes within registration of each individual resolvable spot and increasing the dynamic
range of spectrometer, has to be taken into account as well. The current stage of analysis related to afore-mentioned
problems as well as the results of trial experiments are presented.
Optical design of systems with off-axis spherical mirrors
Show abstract
The astigmatism in reflective imaging systems can be eliminated by a proper configuration. However, the spherical and
coma are the main residual aberrations in third order theory, but the behavior of all aberrations is not yet fully The main
aberration of classical off-axis reflecting systems is primary astigmatism. The astigmatism in off-axis spherical
understood. Expressions for the wavefront aberrations in an off-axis spherical mirror are presented. These formulas are
derived from the optical path difference between an ellipsoid and a sphere, assuming a relatively small pupil and a small
angle of incidence as it will be described with detail. Using the principle of the optical path difference, we developed the
mathematical expressions that describe the third order wavefront aberrations in a two spherical mirror system when the
object is finite.
Holograms of fluorescent albumin
Show abstract
We report the characterization and analysis of photochromic films gallus gallus albumin as a matrix modified
for holographic recording. Photo-oxidation of homogeneous mixtures prepared with albumin-propylene
glycol, to combine chemically with aqueous solution of ammonium dichromate at certain concentrations. We
analyzed the diffraction gratings, through the diffraction efficiency of the proposed material. Also, eosin was
used as a fluorescent agent, so it is found that produces an inhibitory effect, thus decreasing the diffraction
efficiency of the matrices prepared in near-identical circumstances. The work was to achieve stability of
albumin films, were prepared with propylene glycol. Finally, experimental studies were performed with films
when subjected to aqueous solution of eosin (fluorescent agent) to verify the ability to increase or decrease in
diffraction efficiency.
High topographical accuracy by optical noise reduction in digital holographic microscopy
Show abstract
In this work we present a different method to reduce shot noise in phase imaging from digital holograms. An averaging
process of phase images reconstructed with different reconstruction algorithms of the complex amplitude of a phase
object in digital holographic microscopy. We obtain an improved phase image reaching a 29% of shot noise reduction.
We use a single object complex amplitude that is needed to perform our proposal. Also show the corresponding
simulations and experimental results. As phase sample test we used a micro-thin film step surface made at home of 100
nm high of TiO2 on a glass substrate of 4.7 mm thickness, our system was calibrated and traceable to an Atomic Force
Microscope results.
Obtaining the wavefront in the Ronchi test using only one Ronchigram with random coefficients of aberration
Show abstract
It is well known that the Ronchi test can be used to measure the derivative of the optical path difference of a
wavefront [1]. Therefore when the Ronchi test is used to determine the wavefront of the surface under test, two
orthogonal Ronchigrams are required to reconstruct the surface [2]. We present a simple method to recovery the
wavefront with one Ronchigram without using polynomial fit or trapezoidal integration. The recovery of the
aberration coefficients of third order is achieved by assigning random values but controlled in the equation of
the optical path difference (OPD) which is given for a lateral sheared interferometer. Since the Ronchi test can be
seen as a variation of this type of interferometer [3], namely, the OPD for the Ronchi test is given by the difference
between the original wavefront W(x,y) and the sheared wavefront W(x + Δx,y), resulting in the generation of
various Ronchigrams, which are compared with the Ronchigram under analysis. The generated Ronchigram
with lower RMS (Root Mean Square) must have the highest correlation with the Ronchigram analyzed, since the
RMS is inversely proportional to the correlation. For some simulated Ronchigrams which were generated by
introducing Gaussian noise, some results are shown. The proposed method retrieves in a reliable the coefficients of
the polynomial of the analyzed Ronchigram in a reliable and accurate way.
Transverse detection of fluorescence emitted by erbium-doped optical fibers
Show abstract
We describe a simple and precise experimental procedure for the detection of the transverse fluorescence emitted by
excited ions in erbium-doped fibers. The modulation of the optical pump (980 nm) power allows distinguishing between
transverse fluorescence and pump radiated modes in the measured optical signal using a broadband InGaAs detector.
An electro-opto-mechanical device to make diffractive optical elements
Show abstract
Precision machining is as a very precise and effective method for micro-structure optical components fabrication. In this
paper, the mechanical structure of one XYZ and spindle axis of freedom machine with 250 nm of resolution in linear
axes is described, details of the homemade mechanical mounts are given; also components of the electronic system such
as hardware, firmware and software are included in the description.
Design and implementation of a prototype micropositioning and fusion of optical fibers
Show abstract
We developed an automated system in micro and optical fiber fusion, using stepper motors of 3.6 ° (1.8 ° Medium step)
with a threaded system for displacements in the order of microns, a LM016 LCD for User message management, a
PIC16F877A microcontroller to control the prototype. We also used internal modules: TMR0, EEPROM, PWM (pulse
width modulation) control using a pulse opto-cupped the discharge circuit high voltage (20 to 35 kilovolt transformer for
FLYBACK fusion) The USART (Universal Synchronous Asynchronous Receiver Transmitter) for serial interface with
the PC. The software platform developed under Visual Basic 6.0, which lets you manipulate the prototype from the PC.
The entire program is optimized for microcontroller interrupt, macro-functions and is written in MPLAB 7.31. The
prototype is now finished.
Rules for optical metrology
Show abstract
Based on 30 years of optical testing experience, I have defined seven guiding principles for optical testing. This paper
introduces these rules and discusses examples of their application.
Cost modeling for space optical telescope assemblies
Show abstract
Parametric cost models are used to plan missions, compare concepts and justify technology investments. This paper reviews an on-going effort to develop cost modes for space telescopes. This paper summarizes the methodology used to develop cost models and documents how changes to the database have changed previously published preliminary cost models. While the cost models are evolving, the previously published findings remain valid: it costs less per square meter of collecting aperture to build a large telescope than a small telescope; technology development as a function of time reduces cost; and lower areal density telescopes cost more than more massive telescopes.
Wavefront determination using the Ronchi test with synthetic wavelength
Show abstract
In this work we present an efficient proposal to evaluate optical surfaces working at infrared wavelengths based
on the Ronchi test and on the concept of synthetic wavelength. The implementation is performed by using a
spatial modulator (XGA2 SLM) and a white Light Emitting Diode (LED) of 5mm. In order to select distinct
wavelengths, different color filters are employed. Thus, for a given selected wavelength, the surface evaluation
is carried out according to the method of Ronchi, registering two perpendicular interferograms for this color;
the process is repeated for a second wavelength (architecture of this proposal allowed us to test the surface in
more than two wavelengths). Then, an equivalent ronchigram is computationally generated with the registered
data which is then analyzed in order to generate the wavefront for the correspondent synthetic wavelength.
Observations of our results show that with an appropriate LED alignment and high intensity, we avoid an
increase of noise due to the employment of longer wavelengths, as well as the alignment problem, often linked
to the evaluation of infrared (IR) surfaces. The simplicity of the optical setup and low cost materials make this
proposal applicable in the area of optical testing.
Concentration limit for mono-disperse colloids observable with numerical DIHM
Show abstract
Digital In-line Holographic Microscopy (DIHM) is a two-steps microscopy technique that allows for accessing to
complex wave information of the optical field scattered by a sample. Initially, the sample is illuminated by a spherical
wavefront such that the amplitude superposition of the portions of the spherical wavefront scattered and not by sample,
is recorded on a digital camera; the recorded intensity is often referred as in-line hologram. On the second step, a
numerical diffraction scheme is used to emulate the diffraction of a spherical wavefront by the in-line hologram
therefore producing a reconstruction in amplitude and phase of the original object. Due to its evident experimental
simplicity, DIHM is a widely used technique for in-situ applications and more recently on real time measurements. This
widespread employment of the technique introduces the necessity of establishing the practical limits achievable with this
imaging technique. Particularly, for the practical study of mono-disperse colloids, the critical concentration is a relevant
factor to identify, in order to establish the optimal conditions up to which DIHM can successfully work. The
reconstruction step produces a set of intensity images, at different axial distances, containing the information of all the
recorded particles; in large study volumes and high concentrations the number of particles overcome the easiness of
manual processing and therefore evidences the need of implementing more automatic tracking algorithms. In this way
the limits of applicability of DIHM rely on both the experimental configuration and the digital processing. With the use
of a modeling tool for DIHM and a semi-automatic tracking algorithm, a numerical estimation of the concentration limit
for which DIHM can work is proposed, following the analysis for its dependence with the experimental configuration of
the recording process.
Temporal response analysis of a fluorescence-based thermal to visible converter
Show abstract
Today's room temperature microbolometers focal plane arrays are the most widespread technology for the registration of
thermal images. Other attempts to develop detection systems are based on the idea of converting the thermal
information into visible. Thermal to visible converters try to achieve the possibility of "detecting" thermal radiation
with common visible detectors. The development of these converters may provide IR and thermal detection methods for
specific thermal imaging applications without excessive investment. Previously, we have proposed a conversion method
based on temperature dependence of the fluorescence emission of a europium-doped complex. Here, we present the
analysis of the temporal response of the sensing element and we also specify the desirable thermal and physical
characteristics of such element in order to allow thermal to visible conversion in real time. With the analysis of the
frequency response of the EuTTA fluorescence, we find that the emission presents a response that allows dynamic
conversion. Furthermore, we analyze the thermal-transient response of the sensing element of the converter. Based on
heat transfer simulation of a pixel of the sensing element, we establish the characteristics that the thermal design should
fulfill in order to have efficient heat transfer in a dynamic converter.
Quantitative evaluation of a plano-convex parabolic lens
Show abstract
A new design of a null Hartman's screen to test quantitatively a fast plano-convex conic lens is presented. The
design of the null screen is based on the caustic produced by refraction through the lens. Additionally, the null
screen can be used to improve the alignment in optical systems. A quantitative evaluation of medium precision
by using a trapezoidal integration method is presented.
Properties of caustics produced by a conic lens: meridional rays
Show abstract
We derive simple formulas for the caustic produced by a positive convex-plano and plano-convex conic lens
by considering a plane wave incident on the lens along the optical axis. By using these equations a paraxial
approximation for the caustics are provided in both configurations. Also, by using these equations it is possible
to obtain the third order coefficient of spherical aberration. Changing the parameters of the lens (refraction
index, conic constant, radius of curvature, thickness of the lens, etc.) we can modify the shape of the caustic,
furthermore there are cases where the spherical aberration changes from positive to negative when we vary
exclusively the conic constant. A formula for the Principal Surface as a function of the height also is given. We
believe that the method to obtain the caustic that we report is straightforward, obtaining a relationship between
caustics, wavefronts, and measurements of the spherical aberrations.
Sliced-pupil grating: a novel concept for increasing spectral resolution
Show abstract
This paper presents the opto-mechanical design of a novel spectroscopic element - sliced pupil grating - that allows
increasing the spectral resolution while keeping the instrument geometry. The concept is based on "cutting" the pupil
into different slices by placing a number of prisms at the two sites of a VPH grating. The independent beams are guided
through a precise opto-mechanical assembly to assure the recombination of the individual images on the detector within
the available error budget, producing a single spectrum. To probe the feasibility of the concept, we have designed and
manufactured a 3-slice prototype for an already-built spectrograph (Elmer, for the GTC 10-m telescope).
Optomechanical fabrication of EDiFiSE spectrometer
Show abstract
The purpose of this work is to describe some optical and mechanical issues relating to the fabrication of the camera and the
collimator of the Equalized and Diffraction-Limited Field Spectrograph Experiment (EDiFiSE), an instrument which forms
part of a bigger project of the Instituto de Astrofísica de Canarias (IAC), Spain, and that was designed and manufactured
within the facilities of Centro de Investigaciones en Óptica in León, México.
Full Poincaré beams
Show abstract
We describe an analytic formulation that describes the spatial behavior and propagation of a class of fully
correlated beams that span the complete Poincaré sphere. The beams can be constructed from a superposition
of a fundamental Gaussian mode and a spiral phase Laguerre-Gauss (LG) mode having orthogonal polarization.
When the orthogonal polarizations are right and left circular, the coverage extends from one pole of the sphere
to the other in such a way that concentric circles on the beam map onto parallels on the Poincaré sphere and
radial lines map onto meridians. If the beam waists match, the beam propagation corresponds to a rigid rotation
about the pole; a mismatch in beam waist size or position produces a beam in which parallels rotate at different
rates with propagation distance. We describe an experimental example of how a symmetrically stressed window
can produce these beams and show that the predicted rotation indeed occurs when moving through the focus of
a paraxial Gaussian beam. We discuss nonparaxial behavior and end with a discussion of how the idea can be
extended to include beams that not only cover the surface of the Poincaré sphere, but fill the volume within the
sphere.
Improved error-reduction algorithm for designing phase diffractive optical elements
Show abstract
The design of diffractive optical elements (DOEs) to generate a desired light intensity distribution has been
studied in the realm of diffractive optics. Within the proposed algorithms to perform the design and optimization
of DOEs are the iterative Fourier transform algorithms (IFTAs). In this work we are interested in generating a
spot array using an IFTA. We propose a modified error-reduction IFTA which allows us to reach a target error
with high effciency.
Characterization by XDR of amorphous SiCx/c-Si structures at high temperatures
Show abstract
By annealing thin hydrogenated amorphous silicon carbide (a-SiCx:H) films deposited by Plasma Enhanced Chemical
Vapor Deposition (PECVD) on crystalline silicon (c-Si) wafers, pn-junctions with very low inverse saturation current
can be formed. This has been shown in heterojunction bipolar transistors and solar cells with +/- 400°C for this process.
The characterization of these structures indicates that a-SiCx:H films partially re-crystallize during the annealing process
forming Si-nanocrystals embedded in the amorphous film. Understanding this process and further improving the pn-junction
the study of the re-crystallization process by X-Ray Diffraction (XRD) measurements has been done. This
paper deals with the characterization of amorphous SiCx/c-Si structures with 100 and 300 nm thickness measured by
XRD with the temperature chamber with an annealing process at 900°C. Both intrinsic and phosphorus-doped a-SiCx:H films were deposited on a c-Si substrate p-type of 300um-thickness with crystallographic orientation <100>
using the PECVD reactor. From the in-situ measurements using the XDR, the crystallization phase was obtained; this
was done by taking the maximum value of intensity at the dominant peak in the orientation <111> and normalization.
Fitting this with the Avrami-Mehl-Johnson Theory the incubation as well as the crystallization time were obtained to
study the thermally activated process.
Characterization of an experimental arrangement to measure position of particles in 3D with a high accuracy
Show abstract
Single particle position calculation in three dimensions (3D) with high accuracy is the very important in several branches
of science. On the other hand, the use of in-line holography to study very small objects in a dynamic volume is a
technique of importance for scientists and engineers across a variety of disciplines for obtaining information about size,
shape, trajectory and velocity of small objects such as dust particles. However, in general for in-line holography,
accurate determination of the object's position in the optical axis direction is difficult. In order to overcome this
shortcoming, we proposed to use in-line holography set up to record particle images in two orthogonal forward
configurations. In this study, we avoid digital holography reconstruction to calculate particle position. To determine
particle position, the proposed method is based on the calculation of the size and position of the central spot size (CSS) of
a particle diffraction image. The size of the CSS is calculated by using the Continuous Wavelet Transform (CWT) and
Continuous Hough Transforms (CHT), an then the size of the CSS is related to a calibration curve calculated
experimentally in order to determine the "z" particle position and centroid of the CSS render the "x-y" position of a
particle image. The procedure proposed in this work to determine the 3D particle position is so simple since it avoids a
complicated experimental set-up and several computational steps in order to obtain the 3D position of the particles. Our
approach offers the following advantages: First, the mathematical accuracy, light illumination as well as particle and
medium refractive indexes are used during the analysis. Second, it is not required to resolve the size of particle since we
calculate only the size of CSS of a diffraction particle image pattern.
Optomechanical design, analysis, and simulation of tunable liquid-filled lenses
Show abstract
Tunable liquid-filled lens (TLFL) is a lens that changing their focal length by modify the quantity of
liquid within the mount. Recent research shows that, the use of tunables lens makes lighter, simpler and
more compact optical devices in micro-ingineering. In the literature there are papers that present
simulations of the behavior of tunable micro-lenses composed slim membranes. We use a TLFL
composed a cylindrical metallic mount with a compartment for two transparent elastic membranes filled
with water between them. Membranes with plane, spherical and conic surfaces are employed. The
membranes are elaborated of Polydimethilsolixane and the mechanical mount is made of alluminium. In
this work, we present the opto-mechanical design, analysis and simulations of behavior de tunable liquid-filled
lenses composed thick membranes. The analysis is made in three TLFL with different types
membranes. The simulations and analysis of mechanical behavior were made with SolidWork™ software.
Moreover an application with genetic algorithms was development to obtain the geometrical parameters
of the lenses when a value of pressure is applied on the membrane surfaces. On the order hand, the
analysis of optical behavior of the lenses was made with the OSLO software. Finaly, results are shown.
Progress in the design of chromatic null screens to test cylindrical parabolic concentrators
Show abstract
This paper shows the qualitative and quantitative results obtained on the test of cylindrical parabolic concentrators when
the screens are designed using dot color changes to guarantee a better dot correspondence assignment and to make the
optical test of the concentrator easier; the method allows to measure deformations from tenths of a millimeter to several
millimeters, thus demonstrating that null screen method is good enough for testing surfaces with important deformations.
On a second approximation, it is designed a null screen corresponding to the surface evaluated with the first one by
fitting a fourth grade polynomial with crossed terms; with this, it is shown that the first test gets closer to the shape of the
surface validating it.
Analysis of interferograms of a lens using a knife edge interferometer
Show abstract
In previous works Korneev, et al. and Cornejo, et. al. Shown the feasibility to produce an interference pattern, by
setting near by the focal point of a lens a razor knife edge. The interference phenomena is produced between the
wavefront coming from the lens, and the wavefront produced by the knife edge. In this work, such technique is applied
for testing a lens. Since partial interferograms are observed, due to the obstruction of the knife edge to the wavefront
coming from the lens; by rotation of the knife edge in several directions, interferograms with different information can
be registered by means of a CCD connected to a PC. Experimental measurements are given after several interferograms
with different number of fringes were analyzed.
Design of compact multiband satellite imager using a complex mathematical model
Alexandr L. Makarov,
Leonid V. Varichenko,
Nikolay I. Lykholit,
et al.
Show abstract
The article presents original design and fabrication principles and main characteristics of compact 8-m resolution multiband
imager for small satellite. For estimation and obtainment of maximum possible parameters of the imager in spatial resolution and
image quality with strict limits of weight and dimensions of imager a complex mathematical model of imager was developed and
applied, which includes and binds image quality, geometric, energy and probability factor of spatial resolution of the whole section
object-atmosphere-objective-CCD array.
Wavelength measurement with iterative self-imaging phenomenon
J. Garcia-Sucerquia,
Giorgio Matteucci
Show abstract
The wavelength of the electromagnetic radiation plays a key role on determining the spatial resolution an imaging
system can achieve, the way how the wave interacts with matter and how it propagates. For this reason the measurement
of the wavelength associated with electromagnetic radiation of any order is fundamental. For light, simple diffractioninterference
experiments can lead to an appropriate measurement of this feature. For electrons, however, the wavelength
value is calculated simply by the knowledge of the accelerating potential. In this work, we present an iterative method
for measuring the wavelength of electromagnetic radiation of any order. By using the self-imaging effect that arises as an
electromagnetic wave impinges on a periodic object, the wavelength of the wave can be determined. Experimental
results of the application of the method to measure the wavelength of light are shown. The basis for the application of
the method to determine the wavelength of electron waves are settled.
Responsivity determination of a hydrogenated amorphous silicon micro-bolometer array
A. Orduña-Díaz,
M. Rojas-López,
R. Delgado-Macuil,
et al.
Show abstract
We present the characterization of a boron doped hydrogenated amorphous silicon (a-Si:H) thermosensor bolometer
array for far infrared detection. The array was fabricated over a silicon wafer on a 0.4 μm silicon-nitride (Si3N4) layer.
Wet bulk micromachining was used to create pixels of suspended nitride film by removing the silicon underneath. On
this film, a boron doped a-Si:H layer was deposited using a low frequency PECVD system at 540 K. Conventional
lithography was used to define the bolometers on the nitride windows, and the 5 × 5 microbolometer array was fabricated
and characterized at 77 K. A 1.17 x 10-2 mA/W responsivity, with a temperature coefficient of resistance (TCR) of
4.25%, were obtained.
Self-assembled monolayer as optical transducers using spiropyran photochromic material
Alicia Ortiz Ramírez,
Raúl Delgado Macuil,
Marlon Rojas López,
et al.
Show abstract
The self assembled monolayers (SAM) have become in the most popular strategy for design and generate surfaces
characterizing by specific functional organic groups. The aimed of this work is applied this SAM as optical transducer in
biosensors. The techniques, Infrared (in ATR mode) and UV/Vis spectroscopy have been used to study the films
generated in each step in the self assembled process. The SAM was generated as follow; first silane group was added to
the glass substrate. After that, the substrates were immersed in a solution containing carbomiide group (EDC). Finally
the spiropyran 1',3'-Dihydro-8-methoxy-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indole] was attached
to functionalized slides. In each process absorbance was analyzed by UV/Vis (270 to 500 nm) and FTIR (650 to 1800
cm-1). In UV, the spectra shows an absorbance band centered at 280 associated to EDC film and a lower intensity band
centered at 380 nm associated to spiropyran. In FTIR spectra, the Si-Si and Si-O bond are present below the 1250 cm-1.
The EDC film shows very weak bands in the region from 1300 to 1800 cm-1. For the spiropyran film the band associated
to the C-N, N-O, C=C, C-H and aromatic ring have a very well defined peaks. Once the transducer bands were detected,
it was immersed in glucose solution; the infrared spectral show bands are associated to glucose in the transducer.
Interferometric analysis of polishing surface with a petal tool
Alfonso Salas-Sánchez,
Irce Leal-Cabrera,
Elizabeth Percino Zacarias,
et al.
Show abstract
In this work, we describe a phase shift interferometric monitoring of polishing processes produced by a petal tool
over a spherical surface to obtain a parabolic surface. In the process, we used a commercial polishing machine; the
purpose of this work is to have control of polishing time. To achieve this analysis, we used a Fizeau interferometer
of ZYGO Company for optical shop testing, and the Durango software from Diffraction International Company. For
data acquisition, simulation and evaluation of optical surfaces, we start polishing process with a spherical surface
with 15.46 cm of diameter; a 59.9 cm of radius curvature and, with f/# 1.9.
Accurate generation of structure light fields by means of phase synthetic holograms
Show abstract
Structured light fields, defined as laser beams which amplitude and phase distributions have been shaped to
take physical forms with a high degree of complexity, are of great interest in several areas in optics due to their
wide variety of applications. Such fields, in order to maintain their properties, must be generated in the most
efficient and accurate way possible. Phase synthetic holograms (PSH) implemented on liquid crystal spatial light
modulators (LC-SLM), have proved to be a powerful method to generate structured light fields. In this work we
use six different holographic codes that we consider the most representative found in literature, to numerically
evaluate their performance when parabolic beams (PBs) are encoded. Also, we present some experimental results
that are obtained when the holograms are implemented on a liquid crystal spatial light modulator.
Illuminance-spatial-distribution-based total luminous flux determination for white LEDs
Show abstract
Here we report on the application of the well known photo-goniometric method, based on illuminance spatial distribution
direct measurements, to determine the total luminous flux for high-intensity white LED sources; thus testing the
CENAM primary metrology capabilities recently developed to face the increasing needs claimed by the rapidly moving
solid-state lighting industrial sector in Mexico. These first results obtained at CENAM after the gonio-photometric
method implementation, allowed us to determine in good accuracy the total luminous flux for a high intensity white LED
source, with an estimated uncertainty of 2.86 % (k=1); still lower than the claimed by the tested LED manufacturer. We
clearly identified the spectral mismatch correction factor determination and the LED junction temperature measurement
and control as the dominant uncertainly sources, and will be addressed in order to improve the accuracy of the
measurement system for future experiments.
Pulsed lasers in photovoltaic technology
Show abstract
Schottky diodes have been made on both n-type and p-type virgin mono-crystalline silicon processed by three kinds of
pulsed lasers currently used in new photovoltaic technologies. The electrical characteristics of these diodes have been
measured as a function of laser fluence. A strong change in all of their electrical parameters occurs for fluence equal or
higher than a threshold at which the processed silicon surface layer turns into melt. Capacitance versus voltage
measurements and DLTS analyses show that laser irradiations introduce a large density of deep levels related to active
defects in the processed surface and bulk area. These defects are believed mostly generated during the fast quenching
rate in pulsed laser treatments.
Fabrication of a deformable mirror for pulse shaping
Show abstract
In this work we report on a fabrication method for producing large-area multilayer polymer membranes and describe its
application to the instrumentation of a deformable mirror. This implementation allows for highly flexible mirrors in
which mechanical properties vary in a controlled manner in order to better match optical requirements. In addition, the
mechanical properties of such membranes allow for a large number of closely spaced actuators. We report on the
mechanical properties of metal-polymer membranes and discuss their application to pulse shaping experiments.
Optical pressure sensor based on the combined system of a variable liquid lens and a point diffraction interferometer
Show abstract
In this work we present an experimental proposal for an efficient optical pressure sensor based on a Variable Liquid Lens
(VLL) and a modified Point Diffraction Interferometer (PDI). The working principle of the proposed sensor relies on the
fact that a pressure variation induces a change in the lens curvature and hence in its focal length which can be tracked
and measured with the interferometer. The pressure is then measured by recording and processing the interferometric
images. The calibration of the sensor in this proposal demonstrated a working range of 0-26 kPa with an accuracy of less
than 0.1 kPa in the whole range.
Optical testing of the surface quality of a variable focal length lens with null-screens
Show abstract
The null-screen method has been used to test aspheric surfaces. This geometrical method measures the slope of the test
surface and by a numerical integration procedure the shape of the test surface can be obtained. Now, in order to test the
surfaces of a variable focal length lens (VFLL), we propose use a conical null-screen. We present the formulae to design
the null-screen in such a way that the image on the CCD is a perfect array of spots; departures from this geometry are
observed as deformation of the surface. The VFLL is designed in such a way that under conditions of mechanical
equilibrium both surfaces are spherical; however, its shape can be easily modified mechanically changing its radius of
curvature. In order to analyze the shape of the surfaces of the VFLL at different radius of curvature, we evaluate its form
using a conical null-screen. This procedure allows study the deformations of the surface.
New null screen design for corneal topography
Show abstract
In this work we report the design of a null screen for corneal topography. Here we assume that the corneal surface is an
ellipsoid with a diameter of 12 mm and a curvature radius of 7.8 mm. To avoid the difficulties in the alignment of the
test system due to the face contour (eyebrows, nose, or eyelids), we design a conical null-screen with spots (similar to
ellipses) drawn on it in such a way that its image, which is formed by reflection on the test surface, becomes an exact
radial array of circular spots if the surface is perfect. Additionally, we performed a numerical simulation introducing
Gaussian random errors in the coordinates of the centroids of the spots on the image plane, and in the coordinates of the
sources (spots on the null-screen) in order to obtain the conical null-screen that reduces the error in the evaluation of the
topography.
Improving the quantitative testing of fast aspherics surfaces with null screen using Dijkstra algorithm
Show abstract
The null screen is a geometric method that allows the testing of fast aspherical surfaces, this method measured the
local slope at the surface and by numerical integration the shape of the surface is measured. The usual technique
for the numerical evaluation of the surface is the trapezoidal rule, is well-known fact that the truncation error
increases with the second power of the spacing between spots of the integration path. Those paths are constructed
following spots reflected on the surface and starting in an initial select spot. To reduce the numerical errors in
this work we propose the use of the Dijkstra algorithm.1 This algorithm can find the shortest path from one
spot (or vertex) to another spot in a weighted connex graph. Using a modification of the algorithm it is possible
to find the minimal path from one select spot to all others ones. This automates and simplifies the integration
process in the test with null screens. In this work is shown the efficient proposed evaluating a previously surface
with a traditional process.
Dragging force and astigmatic surface in commercial polishing machines
Show abstract
It is well known that astigmatic surfaces are obtained when surfaces are polished in commercial polishing machines,
which are designed to produce surfaces of revolution. The authors of this paper do not know an explanation for this
result.
In order to understand why the wear is a function of the angular position on the glass, we measured the dragging force
applied from a rotating glass to a small fixed tool of Teflon®. These experiments were done for several tool radial
positions by using a table travel X-Y.
With the aid of a force sensor dragging force as a function of the time was measured. We found that dragging force is a
periodic function with fundamental frequency equal to the angular velocity of the glass, indicating that there is more
wear on one glass angular position than another. We also found that this result is independent of the radial position of the
tool. We used a polisher concentration of 20 degrees Baumé which is recommended by the supplier. And the amount of
polisher per time and area units, dragged by the tool, remained constant for each one of the radial positions of the tool.
Quantitative surface evaluation by matching experimental and simulated ronchigram images
Show abstract
To estimate qualitatively the surface errors with Ronchi test, the experimental and simulated ronchigrams are
compared. Recently surface errors have been obtained quantitatively matching the intersection point coordinates of
ronchigrama fringes with x-axis . In this case, gaussian fit must be done for each fringe, and interference orders are used
in Malacara algorithm for the simulations. In order to evaluate surface errors, we added an error function in simulations,
described with cubic splines, to the sagitta function of the ideal surface. We used the vectorial transversal aberration
formula and a ruling with cosinusoidal transmittance, because these rulings reproduce better experimental
ronchigram fringe profiles. Several error functions are tried until the whole experimental ronchigrama image is
reproduced. The optimization process was done using genetic algorithms.
Phase shifting interferometry by modulation of the electric field module
Show abstract
A new method for phase-shifting interferometry based on the wave amplitude modulation is proposed and discussed. This proposal is based on the interference of three waves, where two waves attend as two reference waves and the other wave attends as a probe wave. Whereby, three interference terms are obtained, but because of a phase difference of π/2 between the two references is kept constant, one of the three terms will be dropped while the two remaining will be put in quadrature. Under these conditions the resulting pattern is mathematically modeled by an interferogram of two waves, where an additional phase is given by the amplitude variations of the reference waves. In this paper, both a theoretical model and some numerical simulations are presented
Testing of a convergent optics system off-axis using a Ronchi rule on a nodal bench
Show abstract
In this paper, we propose to use a Ronchi rule on a Nodal Bench to test convergent optics system. The Ronchi rule is of
frequency medium, between 200 and 500 lines/inches. Besides, this test takes advantage to measure nodal plane and
focal distance on-axis and off-axis of some system optics with Nodal Bench. The optics system under test is illuminated
with a plane wavefront and it is focused to focal distance of the optics system under test. Ronchi rule is placed in exit
pupil of optics system, it generate interferograms with the aberrations of optics system. In this interferograms we observe
fines fringes of interference which are generated by the rule frequency like the rule works as a reflections multiples
interferometer. The interferograms are displayed on a computer by a CCD, it is placed on the focal point of the system
under test. We show some preliminary results of this test.
Design and construction of a compact Z-scan portable system
Mónica F. Jiménez-Salinas,
Antonio A. Rodríguez-Rosales,
Roberto Ortega-Martínez,
et al.
Show abstract
The design and construction of a compact instrument that automatically measures Kerr-based third order nonlinearities
(both nonlinear refractive index: γ, and nonlinear absorption: β) in materials, is presented. The instrument includes
control of the polarization state of the input laser beam and was calibrated with well known reference samples. The
mechanical translation system and the polarizer rotation-stage are controlled via a home-made electronic circuit, whereas
the data acquisition from three photodiodes is performed by a National Instruments 12-bits DAQ. The entire system is
fully controlled by means of an application program encoded in LabView. The importance of the developed experimental
device is its reliability, compactness, easy implementation and transport, table-top installation, low cost and high
accuracy.
Off-axis parabolic optical relays: almost perfect imaging
Show abstract
Off-axis parabolic elements have found application in Tera-Hertz imaging and new application in two-photon microscopy scan engines. Both these applications demand spatial and temporal precision in photon location. This modelling work examines how close off-axis parabolic elements are to the perfect image relay by calculating the geometrical performance metrics of spot diagrams, point spread functions and wavefront distortion for different arrangements of off-axis parabolas and a parabolic torus when compared to a close-coupled two mirror scan engine. Results identify the off-axis parabolic elements as a superior scan engine particularly in wide-field scan instruments. When within the optimum beam size versus parabola focus length ratio, the imaging of these systems is superb.
Optical design for MEGARA: a multi-object spectrograph for the GTC
Show abstract
MEGARA is a multi-object spectrograph project for the 10.4m Gran Telescopio Canarias with medium to high
resolution: R ~ 5600 - 17000. The instrument operates in three modes that cover different sky areas and that can run
simultaneously: (1) the compact mode through a large central Integral Field Unit with minimum fiber pitch, covering a
field of view on sky of 12 arcsec × 14 arcsec, (2) the sparse mode with fibers covering 1 arcmin × 1arcmin in three
pointings and (3) the dispersed mode with a grid of nearly 100 robotics positioners able to place 7-fiber minibundles
over a large field of view of 3.5 arcmin × 3.5 arcmin. The spectrograph is composed by a pseudo-slit, where the fibers
are placed simulating a long slit; a slit shutter is placed just behind the pseudo-slit, a collimator, a 162mm pupil where
the volume phase holographic gratings are placed, and the camera with the detector. Here we describe the spectrograph
optical rationale, the conceptual optical design and the expected system performance.
Simulation of the focusing optics of a crossed Czerny-Turner spectrograph for prototypes adjustments
Show abstract
It has been prototyped the basic optics and electronics of a crossed Czerny-Turner spectrograph to work at different
wavelengths. The optical system of the spectrograph prototype has been simulated using OSLO software in order to
optimize the capture of the light spectrum. The study that is presented in this paper is based on the optimization of the
focusing optics orientation that would obtain the smallest y-spot width onto a linear CCD, for different central
wavelengths. It has been changed the orientation of the focusing optics trough the simulation, and changes in the spot
diagram has been observed and plotted. Finally, we have obtained recommendations using these results, how to adjust
the focusing optics in real spectrographs for different central wavelengths. Simulated spectrograph had about 0.25 nm
mean resolution with a focusing optics of 100 mm focal length.
Fractal diffraction elements with variable transmittance and phase shift
Show abstract
The new type of diffraction fractal elements is presented and optical fields properties, obtained from these
elements are discussed. Fractal diffraction elements based on well-known fractals, possess exact or statistical selfsimilarity,
but have managed amplitude transmittance and phase shift, which are correlated with fractal spatial
characteristics. The fractal dimension is not enough for these objects description, and the correlation coefficient between
phase/amplitude and spatial characteristic is needed. For this reason the fractal objects were called multifractal structures
(MFS).
It is shown that the MFS diffraction spectrum possess prevailing power of high frequencies in comparison with
spectra of regular two-dimensional or fractal structures with binary transmittance and phase shift. This property could be
applied for spatial filtering and transparent objects phase heterogeneities detection. Modeling results for different MFS
types are presented and it is shown that MFS application allows detecting the value of initial object distortion with high
accuracy. The description of fractal zone plates (FraZP) with variable transmittance and/or phase shift is also presented.
The results of Fresnel diffraction modeling from FraZPs with MFS show that the correlation coefficient value has
influence on the focal point position.
Calibration of a Shack-Hartmann Sensor (SHS) with a point diffraction interferometer (PDI) to measure the wavefront aberrations of the human eye
Show abstract
To measure the wavefront aberrations of human eyes, a Shack-Hartmann Sensor (SHS) was developed at UNAM-CCADET.
Usually, for calibrating the SHS a well corrected collimated beam is used, so the evaluation of the aberrations
depends on this calibration. We propose to use a Point Diffraction Interferometer (PDI) in parallel with the SHS, in order
to be able to check for aberrations in the calibration beam at any time. This allows reducing the delay between the
calibration and measurement of the aberrations of the eye made with the SHS. In addition, both measurements are made
without moving components, so the evaluation made through the SHS can be compensated with the reference beam
measurement made by the PDI. The results of the quantitative evaluation of the wavefront aberrations of a human eye are
presented in this paper.
Quantification of critical parameters for a rotational shearing interferometer to detect extrasolar planets
Show abstract
There is increasing interest to detect extrasolar planets directly. In the last years, more than 500 planets have been
discovered by means of indirect methods. However, the small signal-to-noise ratio and the small angular separation of
the star-planet system have hindered the direct detection of the optical / IR signals caused by the planets. Several
methods have been proposed to cancel the star irradiance and detecting the presence of the planet around them. One
proposal is the rotational shearing interferometer (RSI). Previously, by exact ray trace, we determined the positioning
tolerances and the resolution of the fine mirror movements needed to satisfy a maximum wavefront deviation of λ/10 (at
633 nm) in the RSI. In this work, we show a method to quantify, employing exact ray trace and the interference pattern,
the critical parameters for this RSI to detect extrasolar planets.
Information Acquisition, Processing, and Display
High-density optical disks for long-term information storage
Show abstract
Optical discs are widely used for storage of archival data represented in a digital form. Long-term storage of information
recorded on standard CDs is provided by periodical rewriting (once in 3-5 years) on the new carriers. High-stable lightsensitive
materials and special reflective metal coatings are proposed to use for increasing the information storage terms
of the optical discs. The conducted researches have showed that the application of vitreous chalcogenide semiconductors
in optical WORM discs assures the data storage terms up to 30 years. Substantially larger terms of data storage can be
realized on the optical ROM carriers. Attainment of the guaranteed data storage terms within several hundreds years is
provided in such carriers by applying high-stable materials substrates and information should be represented in the form
of a micro-relief structure on the substrate surface. Sapphire, quartz, silicon, glass-ceramics and other materials can be
utilized for manufacturing substrates of optical BD discs (and other subsequent high-density disc formats). These materials
allow creating substrates characterized with increased melting temperature, chemical and mechanical resistance.
Furthermore, using the mentioned materials for substrates production permits applying high temperature materials, such
as chrome and nickel, to creation of high-stable refractive layers and demonstrating the sufficient mechanical adhesion
between the refractive layer and the substrate. Modern methods of thermo-lithography offers creating of nano-size images
on photo-resist layer deposited on the substrates. Those images can be transformed to the nano-size relief structures
on the surface of the high-stable materials substrates by techniques of reactive ion-beam etching.
Mirage is the image of an object in the flat ground surface
Show abstract
It is generally accepted that mirage is formed when temperature of the ground surface, in a flat area like desert, is higher
than the temperatures of the over ground air layers. In this case, light emerging from a distant object makes total internal
reflection in the air layers and forms the image of the object that is called mirage. Our investigation on mirage formation
in desert indicates that there is no meaningful relation between mirage formation and temperature change over the
ground. In addition, we show that, the interference of the lights reflected from different air layers destroys the coherency
of the image forming light. This happens because the temperature change occurs in an interval larger than a wavelength.
In the second part of the report we demonstrate theoretically and experimentally that flat rough surfaces behave like
mirrors at very large incident angles. We show that there is a threshold incident angle for observation of image in a rough
surface that depends on the surface roughness and light wavelength. The shortest distance between observer and the
image is determined by the threshold incident angle. Mirage is such an image. Image formation is studied in rough sheet
glass surfaces that prepared by grinding with powders of different sizes.
Image-plane alcove reflection hologram using one-step recording
Yih-Shyang Cheng,
Ting-Ching Lee
Show abstract
Image-plane technique can overcome the annoying "picket-fence" effect encountered in the traditional multiplex
holography. Previously, we have adopted a three-step process to fabricate a reflection-type image-plane alcove
hologram. Here, we design an anamorphic optical system for the object wave which is mixed with light diffracted from
a line segment on a diffuser to simplify the recording process to one step. Experimental result shows single-colored
image reconstructed with white light from LED. Qualitative description of some characteristics of the reconstructed
image is also presented.
Development of fluorescent multilayer disc structure
Ievgen Beliak,
Larisa Butenko
Show abstract
The fluorescent multilayer disc (FMD) consists of a substrate and the sandwich-structure of information and
intermediate layers. While all the structure of the disc is transparent and homogeneous the parasitic signal will be
caused mostly by photoluminescence (PL) and absorption of pits areas where laser light is unfocused. At large
number of layers (10 or more) the noise level will get significant value, so it was suggested to derive readout
signal as a variable one. Also it was proposed to record information only by the lands, to decrease the absorbance
level and thus uncontrolled changing of the noise level. Furthermore in the FMD information layer there are inner
and outside peripheral areas which hold a stable level of parasitic signal during readout from the edges of the disc.
While the PL readout signal is spatially isotropic the optical head of the FMD drive receives just a part of the
probing beam energy. PL quantum yield, absorption factor, receiver systems exposure loss coefficients are other
reasons of the low PL signal. Thus the problem of the low SNR in this case is a major one and the only way of its
solving is synthesis of the dye with a high PL quantum yield. The PL relaxation time on the other hand is a main
feature of the data reading rate and therefore selection of the appropriate recording material will allow to bring
this parameter in accordance to parameters of modern optical discs. To achieve this goal the composite organic
pyrazoline dyes where synthesized and investigated as effective medium with a PL quantum yield up to 60-70%,
relaxation time less than 100 ns, PL wide spectrum and opportunity of two-photon absorption. These parameters
were further improved by a method based on the performance of organic dye molecules in the zeolite matrix.
Optical spectroscopy as a monitor of thin film growth in sputtering
Noemi Abundiz,
Angeles Perez,
Víctor García,
et al.
Show abstract
Line intensity ratio has been used in astronomy to calculate plasma density and temperature. This procedure
is applied to monitor thin film growth in plasma-assisted deposition, it provides very useful information such as
density and temperature of the plasma. The propose of this study is monitor variations of the plasma during
deposition, using wide field optical spectroscopy and establish a relation with thin film stoichiometry. We report
the preparation of inhomogeneous SiOxNy thin films, by sputtering.
Cavity-enhanced direct frequency comb spectroscopy
Show abstract
A Cavity-Enhanced Direct Frequency Comb Spectroscopy (CE-DFCS) setup developed in our laboratory is described.
We focus on the broadband spectrometer which is based on a Virtually Imaged Phased Array (VIPA). It can detect 3500
independent channels simultaneously, covering a bandwidth of 20 nm with a resolution of 800 MHz around a central
frequency of 1.5 μm in a few microseconds. The bandwidth can be extended to 200 nm by rotating the grating of the
VIPA spectrometer.
Infrared laser-based remote sensing system for ambient air quality monitoring
Show abstract
CO2-laser DIAL ozone integrated measurements were performed in Madrid City. The results showed a
dependence of ozone on UVB radiation, abundance of vehicle generated NOX's and hydrocarbons. An average
decrease of 12.0 ± 1.2 % of the intensity of vehicle traffic resulted in a lowering the ozone load by almost 14.0 ±1.4 %. Moreover, measurements of atmospheric ethylene, as a hydrocarbon representative and its relation with
ozone, were performed. Ozone showed the same behaviour namely, a slow increase then reached a maximum at
around 15:00 and back to 40-50 ppb level. The new data can stimulate the development of new local models to
understand the dynamic underlying urban pollution.
Quantitative analysis of metformin in antidiabetic tablets by laser-induced breakdown spectroscopy
Show abstract
Nowadays the production of counterfeit and low quality drugs affects human health and generates losses to pharmaceutical industries and tax revenue losses to government. Currently there are several methods for pharmaceutical product analysis; nevertheless, most of them depend on complex and time consuming steps such as sample preparation. In contrast to conventional methods, Laser-induced breakdown spectroscopy (LIBS) is evaluated as a potential analytical technique for the rapid screening and quality control of anti-diabetic solid formulations. In this paper authors propose a simple method to analyze qualitatively and quantitatively Active Pharmaceutical Ingredients (APIs) such as Metformin hydrochloride. The authors used ten nanosecond duration pulses (FWHM) from a Nd:YAG laser produces the induced breakdown for the analysis. Light is collected and focused into a Cerny-Turner spectrograph and dispersed into an ICCD camera for its detection. We used atomic emissions from Chlorine atoms present only in APIs as analyte signal. The analysis was improved using Bromine as internal standard. Linear calibration curves from synthetic samples were prepared achieving linearity higher than 99%. Our results were compared with HPLC results and validation was performed by statistical methods. The validation analysis suggests that both methods have no significant differences i.e., the proposed method can be implemented for monitoring the pharmaceutical production process in-situ in real time or for inspection and recognition of authenticity.
Study of the dynamical behavior of the LIBS plasma under conditions of low atmospheric pressure
Show abstract
A new arrangement of 3 Langmuir probes to evaluate the electric potential and estimate the electron temperature in the
LIBS plasma is introduced in this work. It consists of three nickel meshes (95% of transparency) on a basis for the
sample in a vacuum chamber. The sample (a 50 cents coin) was analyzed at 9 different pressures (0.2, 0.4, 0.6, 0.8, 1, 2,
4, 6, 8 Torr). Measurements were made of the voltage signal induced in the electrodes relative to one another and to the
sample. Information about the on-time and the duration of the plasma under the decreased pressure conditions can be
extracted from these signals, which could in principle, be also correlated with the velocity of expansion of the plasma
and the establishment of thermodynamical equilibrium in the system plasma-background gas. Additionally, we
photographed the emitted light by LIBS plasma at maximum extension at different pressures by means of two digital
cameras at the right angles to one another and to the laser beam. In each case, the expanded plasma contour was
mathematically analyzed. In particular, the area of the plasma plume as recorded with the cameras was found to follow a
simple relationship with the background pressure in a way not different from an ideal gas.
Flicker reduction in an LCoS spatial light modulator
J. García-Márquez,
E. López-Padilla,
A. González-Vega,
et al.
Show abstract
The spatial light modulators based on liquid crystal (LC-SLMs) have found applications in areas like beam shaping,
optical tweezers, and microscopy. The use of these devices for pupil engineering has been an active research field. Many
experiments with LC-SLMs involve the use of a digital camera, or even an additional LC modulator. Discrepancies in
the refreshing rates of the modulator and the camera, or even between two nominally equal modulators, give rise to
beating and intensity fluctuations, known as flicker, in the point spread function generated by the engineered pupil. In
this paper we present a method for reducing the flicker caused by a liquid crystal on silicon (LCoS) SLM. It consists in
reducing the temperature of the LCoS in a controlled form, in order to increase the viscosity of the liquid crystal, and
with this reduce the amplitude of the intensity fluctuations due to the refreshing mechanism. We demonstrate that the
flicker has been reduced to only the 25% of its initial value, when the LCoS is brought at 0 °C at a given gray level.
Additionally, we found that the proposed reduction of temperature does not affect the dynamical range of phase control.
Gray-level image reconstruction using Bessel-Fourier moments
Show abstract
In this work, we reconstruct discrete image functions by means Bessel-Fourier polynomials. To measure the
image reconstruction we use the Normalized image reconstruction error between the input and reconstructed
images. We show that, a good reconstruction performance is found to be available for gray-level images. The
reconstruction algorithm is implemented using the first forty zeros of the Bessel functions of the first kind.
Experimental results are presented.
Speckle interferometry simulation for sensing heat transmission in ecological buildings
Show abstract
Nowadays people spent a lot of energy to reduce the temperature of walls buildings, by the use of air
conditioner. There are a several solutions using green technologies to save energy, so we need to characterize this kind of
greens technologies. Speckle interferometry is proposed to determine the variation of temperature on green buildings that
relate the efficient use of energy spending in thermal comfort. There is a disadvantage to using thermal resistors sensors
for the analysis of a wall area of sustainable technology, because these items can only measure a very small area, and it is
very slow to make a average measurement of several points to have an estimate of the temperature. The analysis by
speckle is favorable because it is very sensitive to any change made on a surface and this allows us to record the less
obvious variation in the transmission of heat, as we can manipulate to measure considerable size areas. The use of
speckle is more affordable and improve less economical resource than other methods.
Optical system for the supervision of the operation of an induction motor
Show abstract
In this work we present an optical system for the supervision of the operation of an induction motor. We used a Mach-
Zehnder interferometer and cyclic interferometer for the measurement of the vibrations produced by the motor motion
and obtain a frequency spectrum via a Fourier transform of the signal. According to the spectrum, we can know the
operation conditions of the induction motor. The optical system consist of the Interferometer, a data acquisition board
and virtual instrument.
Dammann grating computed-controlled design to profilometry
Show abstract
In this work we have developed a design fringe projection method to obtain profilometry of a suitable object by using Dammann gratings encoded into an LCD as a modulator space and a monochromatic light source. Dammann grating are diffraction binary gratings commonly used to generate diffraction points with the same intensity in Fourier plane. Diffraction order and spatial frequency are parameter of grating design, several gratings types can be designed and projected on objects by controlling parameters of design.
Noise tolerant N-order phase unwrapping system
Show abstract
The present work shows preliminary results of a phase unwrapping technique used in interferometry. Wrapped
phase maps are the result of the modulus 2π ambiguities caused for the phase recovery function arctan. Here
we present a recursive n-order phase unwrapping system that removes the ambiguities, it's robust to noise and
fast. The system is able to recover the unwrapping phase in presence of high noise, according to stability of the
system that can be controlled. This high noise causes line sequential integrations of phase differences to fail.
The system is not numerically-heavy in comparison with other methods that tolerate the noise. The application
areas of the system can be: optical metrology, magnetic resonance, and those imaging systems where information
is obtained as a demodulated wrapped phase map.
Optical Interaction Science
Thermocavitation as a tool for stratum corneum permeation
Show abstract
The cavitation phenomenon has been extensively studied by numerous researchers because the collapse of the
cavitation bubbles is responsible for a number of phenomena of interest in the fields of science and engineering,
such as: Luminescence, sonochemistry, cavitation damage, ultrasonic cleaning, etc. The most common methods
to produce cavitation bubbles are: pulsed lasers, electroforming, sonophoresis, radiofrequency, and Venturi
effect. In this paper we are interested in a method called thermocavitation, which is induced by low power, CW
laser radiation in a highly-absorbing solution of copper nitrate (CuNO4) dissolved in water. The bubble
formation occurs when an overheated region (~300°C) is created followed by explosive phase transition and the
formation of vapor-gas bubbles, which expand and later collapse very rapidly emitting intense acoustic
shockwaves. The characteristic effects of bubble dynamics, in particular the formation, growth, collapse and a
high-speed liquid jet at the moment of collapse are recorded using a high speed video camera (Phantom V7,
Version 9.1) with frame rates of up to one hundred thousand frames/s at different laser powers (62 to 200 mW).
The shockwaves are sufficiently energetic that they may be employed to generate deep lesions in biological
tissue models, such as agar gel and chicken breast samples as a preamble to future studies on thermocavitation
for tissue ablations. This approach of achieving thermocavitation is attractive due to the fact that it is generated
with low power CW lasers which decrease cost and complexity relative to other approaches.
Propagation of ultrashort pulses behind diffracting screens
Show abstract
We study the diffraction of Gaussian pulses and beams within the framework of boundary diffraction wave theory. For the first time the boundary diffraction wave theory is applied to pulsed Gaussian beams, and it is shown that the diffracted field of a pulsed Gaussian beam on a circularly symmetric aperture can be evaluated by a single 1D integration along the diffractive aperture of every point of interest. We compare the theoretical simulations to experimental measurements of ultrashort pulses diffracted off a circular aperture, an opaque disc, an annular aperture, and a system of four concentric annular apertures. Using the recently developed SEA TADPOLE measurement technique, we obtain micron spatial and femtosecond temporal resolutions in the spatio-temporal measurements of the diffracted fields.
Formation of parabolic optical pulses in passive optical fibers
Show abstract
We have investigated a nonlinear pulse reshaping towards parabolic pulses in the passive normal dispersive optical
fibers. We have found that pulses with parabolic intensity profile, parabolic spectrum and linear chirp can be obtained
due to the passive nonlinear reshaping at the propagation distance exceeding a few dispersion lengths. These pulses
preserve parabolic profile during subsequent pulse propagation in a fiber. We have examined the influence of initial
pulse parameters and fiber parameters on the resulted pulse shape.
Effects of primary spherical aberration, coma, astigmatism, and field curvature on the focusing of ultrashort pulses
Show abstract
We analyze the Gaussian temporal envelope of pulses with a duration of 20fs and a carrier wavelength of 810nm at the
paraxial focal plane of an achromatic doublet lens. The incident pulse beam is well-collimated and we use the Seidel
aberration theory for thin lenses. In a set of cemented thin lenses with the stop at the lens, there is only spherical
aberration, coma, astigmatism and field curvature. The distortion aberration introduced by the lens is zero. We analyze
the effect of these aberrations in the focusing of ultrashort pulses for homogenous illumination.
Effects of primary spherical aberration, coma, astigmatism, and field curvature on the focusing of ultrashort pulses: experimental results
Show abstract
We analyze the Gaussian temporal envelope of pulses with an initial duration of 200fs and a carrier wavelength of
810nm at the paraxial focal plane of an achromatic doublet lens designed in the IR region. The Seidel aberrations for thin
lenses are evaluated for a well-collimated beam. We analyze the effect of these aberrations in the focusing of ultrashort
pulses for gaussian illumination and experimental results are presented for 200fs incident pulses and for three incident
angles: 0°, 5°, and 8°.
Tailoring the dispersion of photonic crystal fibers for supercontinuum and photon pairs generation
Show abstract
The interplay between chromatic dispersion and nonlinear effects is patent. Once a photonic crystal fiber (PCF) preform
has been prepared, changing the parameters that control the fabrication process it is possible to adjust the dispersion
properties of the fiber. In addition, it is very useful to develop postprocessing techniques that enable a fine adjustment of
the dispersion along a section of PCF. The tapering of PCF, using a fusion and pulling technique, has been established as
a rather useful technique to engineer the dispersion properties along tens of centimeters. Some of our recent experiments
demonstrate that the use of erbium doped PCF enables an optical control of the dispersion through optical pumping of
the rare earth ions. Our interest is focused on the exploitation of nonlinear PCF for the development of fiber light
sources. Thus, we will present several experiments on supercontinuum and photon pairs generation, through degenerated
four-wave mixing (FWM), in order to illustrate the control that one can achieve on the optical spectra of these light
sources as a function of different dispersion control approaches.
Real-time self-referenced phase reconstruction proposal of GHz-bandwidth non-periodical optical pulses by in-fiber semi-differintegration
Show abstract
We theoretically demonstrate by using fractional calculus tools the linking between the instantaneous phase profile of a
given temporal optical pulse and its photonics semi-differintegration, i.e. a 0.5th-order differentiation/integration. In both
cases, the signal's temporal phase can be retrieved by simple dividing two temporal intensity profiles, namely the
intensities of the input and output pulses of a spectrally-shifted 0.5th-order differentiator/integrator. In both cases, we
obtained simple analytical expressions for the instantaneous frequency profile. We numerically prove the viability of
these proposals.
Model for coherence transfer in a backward optical parametric oscillator
Carlos Montes,
Pierre Aschieri,
Antonio Picozzi
Show abstract
The mirrorless backward optical parametric oscillator (BOPO), where the signal and idler
waves are propagating in opposite directions, will establish a distributed feedback mechanism and
thus optical parametric oscillation without the need to apply mirrors or external feedback to the cavity.
It has been recently demonstrated experimentally by exploiting the periodic poling technique
in second-order nonlinear crystals, that the sub-micrometer structured medium achieves an efficient
quasi-phase-matching of the three wave interaction in the backward configuration. A remarkable
property of such BOPO is the high degree of coherence of the backward wave component, whose
spectrum may be several order of magnitudes narrower than that of the pump, due to the convectioninduced
phase-locking mechanism. Experimentally and numerically proved the transfer of coherent
phase modulations from the pump wave to the parametrically down-converted waves, we show here
that this is also possible for a broad bandwidth spectrally incoherent pump. In order to accurately
describe the nonlinear counter-propagation dynamics of the three dispersive waves, we have developed
for the first time to our knowledge a new numerical scheme which combines the method of the
trajectories usually employed to solve the three-wave interaction and the intraband group velocity
dispersion effect is performed in the spectral domain with the help of the Fast Fourier Transform
(FFT) technique. The model accurately conserves the number of photons and the Manley-Rowe
invariants. This allowed us to predict various configurations of MOPOs in which, thanks to the
convection-induced phase-locking mechanism, a highly coherent backward wave is spontaneously
generated from a highly incoherent pump wave.
Nonlinearity enhancement in rubidium vapor with vectorial mechanism
N. Korneev
Show abstract
We consider the optical nonlinearity enhancement, which is obtained for rubidium vapor by using beams with mutually
orthogonal polarizations. The simple three-level model and numerical estimations for a full transition model are reported.
Different from the traditional Kerr nonlinearity, the vectorial mechanism nonlinearity strength diminishes for higher
intensities, as well as for low ones, and optimal intensity level exists.
Study of a figure-eight laser generating noise-like pulses with adjustable characteristics
Show abstract
In this work we study experimentally and numerically a passively mode-locked figure-eight fiber laser that includes a
polarization-imbalanced Nonlinear Optical Loop Mirror (NOLM), whose switching power can be adjusted through a
wave retarder plate. The laser emits broadband noise-like pulses with a bandwidth that can exceed 50 nm. The pulses are
actually sub-nanosecond wave packets with an inner fine structure of sub-ps pulses with random amplitude and duration.
The duration of the pulses as well as their spectral width can be adjusted through the variation of the NOLM switching
power. Numerical simulations are in good agreement with experimental results, confirming in particular the strong
dependence of the pulse properties on the value of the NOLM switching power, although NOLM switching alone does
not explain the appearance of the noise-like pulsing mode. The properties of this kind of pulses, like their wide
bandwidth and energy, make them attractive for applications like supercontinuum generation and metrology.
Spectral-phase-influence-matrix to shape femtosecond pulses
Show abstract
In this work, we analyse the use of a micro-machined deformable membrane mirror (MMDM) to shape femtosecond
pulses. We present the Spectral-Phase-Influence-Matrix constructed by an inversion method. Spectral-Phase-Influence-
Matrix represents a novel and direct method to estimates the Spectral Phase design from a given actuator voltage settings
in a single step. Numerical and experimental results are presented.
Optical waveguide writing in photochromic material: photoinduced optical properties by femtosecond laser pulses
Show abstract
We report on the interaction of high repetition rate (MHz) Ti: sapphire laser pulses with a spiropyran polymer (MIC1).
Such a polymer is photochromic, wich has potential applications in integrated optical devices. A thin film of polymer
deposited on a glass substrate is irradiated with ultrashort pulses (66 fs) from a Ti: sapphire laser. We demonstrate that it
is possible to induce an absorption band in the visible by the use of femtosecond pulses via a two-photon excitation
process; this might be useful to accomplish waveguide-like structures formation with photochromic response.
Photoluminescence properties of copolymers derived of 3-alkylthiophenes and thiophenes containing NLO chromophores
J. Castrellon-Uribe,
M. Güizado-Rodríguez,
C. M. Rueda-Anaya
Show abstract
In this works, synthesis and evaluation of the luminescence properties of novel polythiophenes derivatives derived of 3-
alkylthiophenes (alkyl=hexyl, octyl) and thiophenes functionalized with a NLO chromophore: 2-[Ethyl[4-[2-(4-
nitrophenyl)ethenyl]phenyl]amino]ethanol are reported. The optical response of copolymers films obtained by spin
coating technique when they were excited optically was analyzed. The fluorescence signals measured to about 650 nm
when the copolymers were excited at 488 nm (blue light) were studied to different excitation powers. The optical
response of the copolymers films shows a change ratio of around 6%/mW. The evaluations of photoluminescence
properties of conjugated polythiophenes are important due to their potential applications in light-emitting diodes (LEDs),
solar cells and chemical sensors.
A model for light transmission through a thin nonlocal-nonlinear media
E. V. Garcia Ramirez,
M. L. Arroyo Carrasco,
M. M. Mendez Otero,
et al.
Show abstract
The transmission of an intense light beam through a thin nonlinear sample has been extensively studied, like in self
phase modulation experiment and Z-scan technique, with different approaches: the Gaussian decomposition method, the
Huygens-Fresnel principle, the diffraction theory, etc., The nonlocality in the response of the media in general leads to
solve more than one differential equation. In this work we present a simple model to calculate, in a numerical way, the
on axis far field intensity in a Z-scan experiment or the far field pattern in spatial self phase modulation experiment by
means of the diffraction theory and taking into account the locality of the thin nonlinear media. The obtained results
show that the peak-valley separation distance and the transmittance difference in a Z-scan experiment and the number of
rings, size and intensity distribution of the far field pattern in the spatial self phase modulation experiment are functions
of the locality in the nonlinear response of the media. The proposed model describes in good approximation
experimental results for samples, like absorbing liquids, liquid crystals, metal nanoparticles, etc., with different kind of
nonlinear response. This model is valid for any value of the nonlinear phase shift.
Photoluminescence increment of Si nanocrystals in presence of Ag nanoparticles
Show abstract
Plasmonics is the most promising field appointed to continue the predictions of the Law of Moore as well as for the
confinement of light on a subwavelength spatial scale, allowing the breaking of the diffraction limit. In that direction, we
have produced by ion implantation, interesting nanocomposites with very attractive optical properties. Recently, a double
implantation of Si and Ag ions in silica, with subsequent thermal treatments in appropriated atmospheres, allowed us to
obtain two layers: one of Si nanocristals (NCs), and other of Ag nanoparticles (NPs). This arrangement shows an
enhancement of the emission of Si nanocrystals (NCs) in a new, totally integrated configuration. The synthesis of the
system by ion implantation offers a total protection of the optical active agents from environmental effects such as
oxidation, additionally assuring a high degree of homogeneity.
We present a photoluminescence excitation study (420-500 nm) of Si NCs, with and without the presence of Ag
nanoparticles (NPs), both embedded in a matrix of SiO2. The level of saturation for Si NCs is independent of the
excitation wavelength, but for Si NCs in the presence of Ag NPs, a saturation level arises for excitation wavelengths near
the absorption band of the surface plasmon resonance of the Ag NP (325-475 nm). The increase of both, the values of
saturation and excitation cross-section of Si NCs in the presence of Ag NPs, is an evidence of the optical interaction
between the metal NPs and Si NCs studied in this work. This suggests a decrease of the lifetime of Si NCs
photoemission due to the interaction with the Ag NPs.
Corona poling assisted second harmonic genertion in nanostructured polymethylmetacrylate films
Show abstract
Films made of Polymethylmetacrylate (PMMA) and doped with dipolar second order nonlinear optical chromophores
were studied by UV-visible spectroscopy and transmitted resonant Second Harmonic Generation technique. The
chromophores were non-centrosymmetrically oriented by a Corona poling field. The UV-visible spectra were measured
in poled films at normal incidence as function of their poling temperatures (60, 80 and 100°C) and they were analyzed in
terms of the Second Order Parameter (A2). The Second Harmonic Generation (SHG) signals in the films were measured
in-situ as function of the poling time at several incidence angles for each poling temperature. The stability of the SHG
signal was also determined, by turning off the Corona field but leaving the films at their original poling temperature. The
films were of two different kinds: amorphous and nanostructured. All the films doped simultaneously with chromophores
and surfactants showed long-range ordered nanostructures. Two kinds of surfactants were used during the synthesis of
the films: ionic and neutral, both of them induced long-range order in the structure of the PMMA, but only some of the
nanostructured films exhibited enough large SHG signals. The second order nonlinear optical response of the
nanostructured films was compared with the corresponding response of the amorphous films. The long-range order in the
films was detected by X-Ray Diffraction (XRD).
The world of attoseconds: where a second lasts as long as the age of the universe
Reinhard Kienberger
Show abstract
The observation of ultrafast fundamental processe in real time is a key to exploring the dynamic behaviour of matter. In
order to be able to do these observations, pulses shorter than the processes under scrutiny have to be generated. Over the
past decade novel ultrafast optical technologies have pushed the duration of laser pulses close to its natural limit, to the
wave cycle, which lasts somewhat longer than one femtosecond (1 fs = 10EXP-15 s) in the visible spectral range. About
ten years ago these pulses were used to generate single isolated attosecond pulses in the extreme ultraviolet (XUV):
Atoms exposed to a few oscillation cycles of intense visible or near-infrared light are able to emit a single electron and
XUV photon wavepacket of sub-femtosecond duration. Precise control of these sub-femtosecond wavepackets have been
achieved by full control of the electromagnetic field in few-cycle light pulses. These XUV pulses together with the
few-cycle (few-femtosecond) laser pulses used for their generation have opened the way to the development of a
technique for attosecond sampling of electrons ejected from atoms or molecules and solids.
Novel properties of soliton-plasmon interactions
Show abstract
We present the numerical modeling of the interaction between a spatial soliton and a surface plasmon polariton under
leak and strong coupling in the following two cases: at metal/dielectric/Kerr structures and metal/Kerr structures in 1D.
Here, we solved the vectorial and nonlinear wave equation using a novel iterative method based in self-autoconsistency,
and we found two kinds of nonlinear stationary solutions called odd and even modes. On the other hand, the propagation
of the stationary solutions is performed for the metal/Kerr system, and quantitatively it shows that odd modes are more
stable than even modes when the spatial soliton and surface plasmon are strongly coupled. Also, we analyzed the
influence of the dielectric layer between the metal and Kerr media, and we discuss their implication and feasibility for
applications in photonic nanodevices. Additionally, the advantages and disadvantages of the numeric method used to
obtain the stationary solutions are discussed. The results obtained in this work are reproducible and contributes with new
information for the development of power-tunable photonic nanocircuits based in nonlinear plasmonic waveguides.
Gauss-Legendre quadrature method used to evaluate the electric field envelope of ultrashort pulses in the focal region of lenses
Show abstract
We analyze the Gaussian temporal envelope of pulses with an initial duration of 10fs and a carrier wavelength of 810nm
along the optical axis of an achromatic doublet designed in the IR region with numerical aperture 0.15 and focal length
of 40mm. The diffraction integral is solved by expanding the wave number around the carrier frequency of the pulse in a
Taylor series up to third order, and then the integral over the frequencies is solved by using the Gauss-Legendre
quadrature method. The numerical errors in this method are negligible by taking 96 nodes and the computational time is
reduced by 95% compared to the integration method by rectangles. We will show that the third-order GVD is not
negligible for 10fs pulses @810nm propagating through the low numerical aperture doublet and its effect is more
important than the propagation time difference, PTD. This last effect, however, is also significant.
Quantum security in homodyne reception using weak coherent states
Show abstract
We present an experimental 8-port Balanced Homodyne Detector at 1550 nm wavelength, operating in free space,
implemented with polarization devices to produce a circularly polarized local oscillator, splitting its In-Phase and
Quadrature components to beat separately with the weak coherent incoming signal. This allows the simultaneous
measurements of the 2 quadratures at the price of an additional noise due to the vacuum fields that leak via the unused
ports, resulting in a modified Husimi function for joint probability distribution for the quadrature components. These
schemes require the proper optical phase synchronization between the local oscillator and the incoming field, which
constitutes a challenge for weak coherent state reception. To achieve this we designed and implemented an optical
Costas loop; the feedback loop (especially the loop filter) which is a result of the optimal design has an impact on the
mutual information between transmitter and receiver, being this parameter a condition to generate the cryptographic key.
We present experimental and theoretical results on the performance of the mutual information between the transmitter
and the receiver due the phase error for different photon numbers.
Numerical study of the medium thickness in the Z-scan technique
Show abstract
The optical characterization of nonlinear media through the Z-scan technique considers initially a thin
medium (with a thickness much less than the beam depth of focus). It has been observed that increasing the
thickness of the medium the transmittance increases, this means that n2 increases, for this reason we will
present a numerical model to determinate the minimum thin and the maximum thick medium limit. A thin
medium is considered as a thin lens with focal length F1 and a thick medium can be regarded as a set of such
thin lenses set with focal lengths F2, these lenses are contained in a medium whit a refraction index different
than air. This analysis is made through Matlab using the theory of Gaussian beams, ABCD matrices and the q
parameter, elementary theory in the development of this work, where the main feature of this model is that the
nonlinearity type of the medium is considered as an integer constant in its focal length3. We present the
graphs obtained from Z-scan for thick medium with both thermal and Kerr nonlinearities.
Amplitude and frequency properties of a four-phonon Bragg anomalous light scattering in a uniaxial crystal with spatial optical dispersion
Show abstract
We study, theoretically and experimentally, a new type of a multi-phonon Bragg light scattering in an optically
anisotropic medium. A four-phonon Bragg anomalous light scattering in a tellurium dioxide crystal was observed using a
light-blue optical beam of about 1 W in power from an argon gas-laser. Just the Bragg regime of light scattering was
assured experimentally and a pentet of the light orders was distinguished and investigated.
Nanoparticle coated optical fibers for single microbubble generation
Show abstract
The study of bubbles and bubbly flows is important in various fields such as physics, chemistry, medicine, geophysics,
and even the food industry. A wide variety of mechanical and acoustic techniques have been reported for bubble
generation. Although a single bubble may be generated with these techniques, controlling the size and the mean lifetime
of the bubble remains a difficult task. Most of the optical methods for generation of microbubbles involve high-power
pulsed laser sources focused in absorbing media such as liquids or particle solutions. With these techniques, single
micron-sized bubbles can be generated with typical mean lifetimes ranging from nano to microseconds. The main
problem with these bubbles is their abrupt implosion: this produces a shock wave that can potentially produce damages
on the surroundings. These effects have to be carefully controlled in biological applications and in laser surgery, but thus
far, not many options are available to effectively control micron-size bubble growth. In this paper, we present a new
technique to generate microbubbles in non-absorbing liquids. In contrast to previous reports, the proposed technique
uses low-power and a CW radiation from a laser diode. The laser light is guided through an optical fiber whose output
end has been coated with nanostructures. Upon immersing the tip of the fiber in ethanol or water, micron-size bubbles
can be readily generated. With this technique, bubble growth can be controlled through adjustments on the laser power.
We have obtained micron-sized bubbles with mean lifetimes in the range of seconds. Furthermore, the generated
bubbles do not implode, as verified with a high-speed camera and flow visualization techniques.
Partial spatial coherence and polarization properties of surface plasmon fields
Andreas Norrman,
Tero Setälä,
Ari T. Friberg
Show abstract
We analyze theoretically the (spectral) spatial coherence and polarization properties in fluctuating surface plasmon
fields generated at a lossy, thin metal film surrounded on both sides by air. Using rigorous electromagnetic
interactions at the interfaces and the theory of optical coherence in 3D fields, we show that new coherence and
polarization effects may occur in such plasmon fields. In particular, coherence lengths extending over several
thousands of wavelengths, or coherence lengths significantly shorter than the wavelength of light in vacuum, can
be found at certain frequencies. Using a recent 3D formulation, we also examine the degree of polarization in
such random surface plasmon fields. We show that the field may be partially polarized in the immediate vicinity
of the excitation of the surface plasmon modes, even though it is fully polarized farther away. In addition, we
demonstrate that an increasing number of modes leads to a more polarized field above the plasmon excitation
region, with the degree of polarization effectively independent of the height.
Two-photon temporal self-imaging
Show abstract
We describe and theoretically analyze the self-imaging Talbot effect of entangled photon pairs in the time domain.
Rich phenomena are observed in coherence propagation along dispersive media of mode-locked two-photon
states with frequency entanglement exhibiting a comblike correlation function. The observed effect suggests a
straightforward and implementable way to transfer remotely frequency standards embedded on ultracompact
quantum light sources.
Radiation forces on Au nanoparticles considering infrared beams
Show abstract
The radiation pressure forces for Au nanoparticles in the Rayleigh regime under the influence of a coherent source of infrared light from 0.7-1.5 μm of a Gaussian beam with fundamental mode corresponding to the TEM00 mode are studied. An intensity distribution of the source in terms of the spot size and power are considered to analyze the gradient, scattering and absorption forces on a sphere located arbitrarily on a Gaussian beam. The results have shown, through an analysis stability, the optical manipulation is better suited for longer wavelengths, small particles, and a beam waist significantly reduced.
Wave propagation in a multiple interfaces nanowaveguide
Show abstract
The multiple functions and potential applications of nanotechnology have become a necessary and powerful tool in
scientific work everyday. Nanotechnology is interdisciplinary science involving physics, chemistry, biology, materials
science and wide range of engineering disciplines. His versatility has led to an increasing use in wide range of fields. For
example, electronic engineering has shown an interest growing in the design of nanodevices due to continued
miniaturization of them. The investigations have focused on the manufacture of electronic circuits and their applications
complex systems, in addition to this, nanotechnology already plays an important role in
development of new materials with tailored features and chemical properties, so their study is important today.
Nanosensors have been under investigation for some institutions in recent years. A nanosensor is a device built on an
atomic scale based on measurements nanometers, whose purpose is mainly to obtain data on the atomic scale transfer so
they can be easily analyzed. In this work We study wave propagation in a low-dimensional planar nano-waveguide, to
establish the principle of operation of an optical structure to propose the design of a nanosensor.
Femto-, pico- and nano-second refractive nonlinearities exhibited by Au nanoparticles
Show abstract
Gold nanoparticles (AuNPs) have proven to be powerful tools in various ultrafast photonic, plasmonic and nanomedical
applications. Numerous advances in the use of AuNPs include research on their interesting and remarkably fast changes
influenced by Surface Plasmon Resonance excitations. Within this work we report theoretical and experimental results
for the physical mechanisms that originate a nonlinearity of refractive index during different temporal regimes for a
high-purity silica matrix containing Au nanoparticles. The nanocomposites were prepared by ion implantation into a
silica matrix, followed by a thermal annealing. We used an optical Kerr gate with 80 fs pulses at 830 nm and a vectorial
self-diffraction technique with 26 ps and with 7 ns at 532 nm in order to investigate the magnitude and response time of
the resulting third order nonlinearity. In all cases we were able to measure and identify an electronic polarization
responsible for the nonlinear refraction. For the pico- and nano-second near resonance irradiations, a contribution of a
thermal effect could be stimulated and then the optical Kerr response enhanced. The presence of saturable absorption for
the pico- and nano-second experiments was measured. We observe that our samples behave like waveguides in the near
infrared spectrum and we estimate that they posses potential applications for all-optical switching devices.
A particle-like model for soliton propagation in optical lattices
Show abstract
We present a simplified model for describing the propagation of optical solitons through optical lattices. A pair
of second order differential equations for the transverse coordinates of the intensity centroid of the soliton are
deduced from the nonlinear Schr¨odinger equation. As an advantage over the quasiparticle approach we avoid the
need of integrating algebraically the soliton intensity profile over the lattice. This allows modeling soliton motion
even for non-symmetric lattice potentials, as that presented by an outer ring of a modulated Bessel lattice . We
discuss in detail the range of applicability of our model and use it to predict the soliton motion in optical lattices
generated by plane-waves, Bessel beams, and others.
Nonlinear optical response of silver nanoparticles and silicon quantum dots
L. Tamayo-Rivera,
R. C. Fernández-Hernández,
J. Bornacelli,
et al.
Show abstract
We present a nonlinear optical study using standard Z-scan technique at the picosecond regime, in a nanostructured
material containing both quasi-spherical silver nanoparticles and silicon quantum dots, and comparing its response to
those from similar systems, one with only silicon quantum dots, and another with only silver nanoparticles. The study
was done using different wavelengths, 355 nm and 532 nm, which are localized at both sides of the surface plasmon
resonance of the Ag nanoparticles, and 1064 nm, which is localized well far away of it. In general, we have observed that
the larger optical nonlinear response came from the sample with silver NPs. However, the combined system showed a
positive nonlinear refraction below the plasmon resonance (355 nm), changing to a negative value for wavelengths above
resonance (532 nm and 1064 nm). We observed also, for the combined system and for the three wavelengths used, a
saturation of the nonlinear refraction index as a function of the incident irradiance.
Linear and nonlinear optical properties of metallic nanocrystals in sapphire
P. E. Mota-Santiago,
A. Crespo-Sosa,
J. L. Jiménez-Hernández,
et al.
Show abstract
In this paper we report the linear and non-linear optical properties of metallic nano-clusters in α-Al2O3 fabricated by ion
implantation (from 2 to 8×1016 ions/cm2). Thereafter, the samples were annealed at temperatures from 600 to 1100 °C in
oxidising, reducing atmospheres. Once spherical nano-particles were synthesized, the samples were further irradiated
with Si+++ with different energies and fluences to control the achieved anisotropy. As a result of the ion implantation
mostly F+ color centers were formed. After thermal annealing they capture an electron to form F centers or combine to
form a F2+ center. Also, the photoluminescence signal from Al+ interstitials appears. Regarding the non-linear optical
response, the spherical-like Au nano-crystals embedded in sapphire show a positive non-linear absorption at 355 nm and
negative non-linear absorption at 532 nm, which shows saturation when increasing the incident irradiance. They also
present positive non-linear refraction at 532 nm, which is null at 355 nm. For the anisotropic systems, a larger
birefringence than natural values was measured in the visible range by ellipsometry means.
Self-focusing mechanism in nematic liquid crystals with sub-millisecond response
Show abstract
Fast optical self-focusing has been observed in a homeotropic nematic liquid crystal cell. This nonlinearity is induced by
an intensity modulated infrared laser having a peak power of 160mW, a pulse repetition rate of 150Hz, and a duty cycle
of 0.05 and launched with extraordinary polarization. During these experiments the illumination time is kept at 0.3msec
and the ambient temperature is controlled. We have observed that self-focusing propagation depends on ambient
temperature, laser power and duty cycle. Notably, when illuminating with a continuous beam having the same
corresponding average power, only diffraction can be observed. These results suggest that the nonlinearity is produced
by a combination of thermal effects and molecular reorientation that leads to changes in the order parameter. Further
optical experiments and thermal calculations have been conducted to identify the responsible mechanism for the self-focusing
of the laser beam. It has been found that soliton formation can be achieved if the parameters as ambient
temperature, pulse repetition rate and duty cycle of the laser are set to optimal conditions. Although, this nonlinearity in
a liquid crystal cell has been already demonstrated for transverse illumination, the presence of beam propagation with
self-focusing has not been reported yet. The fast nonlinearity reported in this work has the potential to generate a number
of new applications of liquid crystals.
Two prisms transmission enhanced by whispering gallery modes: absorption effects
Show abstract
Resonant cavities based on whispering gallery modes (WGM) have high quality factor, Q. This property is highly
desirable for the design of a variety of devices. The quality factor is larger for larger systems, but, at the same time the
density of modes increases, and not as regularly spaced frequencies, because modes of different kind superpose. For a
dielectric cylinder, the modes are characterized by their azimuthal and radial behavior. The complex frequencies
corresponding to the modes have a strong dependence on the radial order. We use the finite difference time domain
method, to study the transmission of light by two prisms with a dielectric cylinder between them. The system acts as a
filter with sharp peaks of modes of high Q. The coupling to the modes can be controlled by changing the distance of
separation between the prisms. For large coupling, the full width at half maximum of the transmission peaks increases,
being more noticeable for the high Q modes.
Optical properties of fullerenes confined in ordered alumina nanotube arrays
Show abstract
In the present work, oxalic amorphous porous anodic alumina membranes (AAM) with highly ordered porous arrays and
average nanometric porous dimensions of 70 nm in diameter and 37 microns in depth (nanotubes) were prepared and
successfully used as hosting matrix for C60 and C70 fullerene compounds. Atomic force microscopy (AFM) studies were
performed on the hybrid samples in order to explore surface morphology and optimal insertion of these molecular
systems into the AAM environment. The cubic nonlinear optical (NLO) properties, such as nonlinear refraction and
absorption of the hybrid samples were studied via the Z-Scan technique in order to evaluate their NLO-performance.
Hybrid AAM with fullerene compounds have shown outstanding NLO-activity with positive NLO-refractive
coefficients.
Entanglement of formation of pair of quantum dots
Show abstract
The Entanglement of quantum systems is a key aspect in order to understand the dynamics and behavior of mixed
systems (density matrix) as bipartite systems of quantum bits (q-bits). A quantifiable measure widely used is the
"entanglement of formation" of a mixed state, defined as the minimum number of singlets needed to create an ensemble
of pure states that represents the density matrix of the system. Considering a double quantum dot system coupled cavity
type Jaynes-Cummings investigate the entanglement between two quantum dots, immersed each in its own cavity,
showing analytically that entanglement has a very interesting effects such as temporal evolution including the so-called
sudden death effect.
NLO characterization for novel borinates: evaluation of the N-B bond
Show abstract
The following work presents the linear and nonlinear optical (NLO) properties for two ligands (L1-L2) derived from cinnamaldehyde and their corresponding boron complexes (B1-B2). These organic molecules have a backbone with electronic π-systems possessing different "push-pull" features. The structure confirmation of compounds L1 and B1 was made through X-ray diffraction analysis, wherein is observed that planar conformation is conserved after boron complexation on B1. Linear absorption of ligands and boron complexes shows a red shift after boron complexation which could be attributed to more efficient intramolecular charge transfer. Second and third-order NLO responses were performed by Electric Field Induced Second Harmonic (EFISH) Generation technique at 1.9 μm and Third-Harmonic Generation (THG) at 1.9 and 1.067 μm, respectively. Experimental results showed an increment on the hyperpolarizabilities values from ligands to boron complexes which are attributed to N→B coordinative bond. The first hyperpolarizability increased by factors of 3 and 2 from L1 to B1 and L2 to B2, respectively. Individually, these studies demonstrate that B1 is the strongest NLO compound, showed values of first hyperpolarizability 126×10-24 and second hyperpolarizability 35×10-24.
Properties of the near field interactions produced by spherical nanoparticles
Show abstract
In the aim to understand the nature of the propagation of an electromagnetic field in
the near region, we study the interactions between an evanescent field and two
different samples of spherical dielectric nanoparticles, i.e. a set of five particles and
a single one. Each sample was studied in separated experiments. This is made by
using a Photon Scanning Tunneling Microscope (PSTM) in the constant distance
mode. We also analyze the obtained images and determine that the optical images
show mainly interference between the evanescent field and the reflected field on the
surface of the nanoparticles. Finally, we found that the perturbation of the
evanescent field, produced by imperfections on the substrate, is negligible in
comparison with the interactions intensity.
Optical spectroscopy and high pressure on emeralds: synthetic and natural
Show abstract
Emerald, natural and synthetic, are the subject of study by means of optical spectroscopy techniques. Particularly,
natural emeralds have been considered as a gemstone in jewelry not being so the synthetic ones. But, in general, the
properties of these are very good for applications, for instance as a laser system, due to the impurities control. In this
work a comparison between natural and synthetic emeralds is done. Chromium ions are the main responsible of the
characteristic fascinating green color of these gemstones, entering in the crystals in octahedral sites. Absorption at room
temperature show up two broad bands in the visible region and two narrow bands called the R-lines. That spectrum
corresponds to trivalent chromium ions in an octahedral site, as it happens in ruby and alexandrite. On other hand,
photoemission arises in the range 640-850 nm. at room temperature . It is shown that the luminescence spectra changes
as the temperature is lowered. The effect on the main peak of luminescence when high pressure is applied on small
samples of emerald shows as a linear function.
Photophysical properties of metallic-phthalocyanines dispersed in sonogel optical glasses
Show abstract
Phthalocyanines (Pc) based compounds having central metallic atoms of Ni were successfully embedded in
mesoporous silica gels via a catalyst-free sol-gel (sonogel) process in order to fabricate optically active solid-state
hybrid glasses in both bulk and thin film formats at different dopant concentrations. The organic-inorganic
hybrid composites obtained at room temperature processing showed stable mechanical
performance, controllable geometrical shapes, good transparency and homogeneity suitable for linear and
nonlinear optical (NLO) characterizations. Hybrid samples were studied via the NLO third-harmonic
generation (THG) technique. AFM studies, epi-microscopy surface evaluation, refractive-index measurements
and UV-Vis spectroscopy studies were also performed in selected bulk and film samples. The morphological
and spectroscopic results showed a homogeneous dispersion of the organometallic compounds within the
highly pure SiO2-sonogel network. Moreover, Brewster's angle measurements have demonstrated the
feasibility of tuning the refractive index of the samples by varying the chromophore dopant concentration.
Additionally, the electronic absorption spectra showed band shifts in the two characteristic bands of the
organometallic compound within sonogel environment, which evidence the formation of molecular H-aggregates
for the developed hybrids and the consequent modifications of their optical properties. Finally,
THG measurements in hybrid film samples exhibited an important NLO activity. We conclude that the optical
effects of these composites can be tuned as function of the nickel-Pc concentration and that the sonogel matrix
mainly acts as an inert protective shell, giving stable mechanical and thermal properties to the guest dopant
compounds.
Mie scattering of light with orbital angular momentum by nanoparticles
Show abstract
We generalize Mie scattering theory to describe the scattering of light with orbital angular momentum (OAM).
We apply our results to the analysis of scattering by gold nanoparticles and compare the angular distribution
of the scattered light for plane waves and light with OAM. The multipole expansion for scattered OAM waves
depends on the localized surface plasmon modes that can couple to incident light carrying a well-defined amount
of azimuthal charge (or l-number) at a particular wavelength. We study here the properties of Mie scattering
of OAM waves by nanoparticles located at the beam waist as a function of the size of the particle and of the
frequency and content of azimuthal charge of the incident wave.
Supercontinuum generation in higher order modes of photonic crystal fibre
Show abstract
Soliton behaviour in higher order electromagnetic (EM) modes in commercial highly nonlinear photonic crystal fibre
(PCF) was investigated by mapping spatial and spectral emission. A femtosecond mode-locked Titanium:Sapphire laser
was used to generate supercontinua within a set of higher-order electromagnetic modes by piezoelectric control of the
spatial field input to the PCF. Coupling pump wavelengths within the normal dispersion regime for the fundamental EM
mode into higher EM modes resulted in the emission of blue light, characteristic of higher order soliton fission, in higher
order EM modes. Detailed spectral measurements across the spatial mode field output from the PCF, showed different
spectral components of the generated continua occupying different spatial electromagnetic modes. In particular, the blue
emission was found to be structured with spectral wavelengths at 440 nm and 450 nm associated with different spatial
EM modes.
These new measurements are the first to detail high order solitonic interactions in higher order electromagnetic modes
and to record different spectral emission wavelengths associated with different higher order spatial modes. These results
are not well matched to current theoretical models for supercontinuum generation developed for the fundamental EM
mode. The lower zero dispersion wavelengths associated with higher EM modes in PCF enable previously undetected
engagement of these modes in supercontinuum generation and propagation.
Photonics and Opto-Electronics
Improvements amplification parameters for radio over fiber of signal 54 MGz
Show abstract
This paper we analyzed three alternatives for optical amplification used to extend the reach of optical
fiber link for the transport of RoF (Radio over Fiber) in view of 54 MHz RF signals for wireless
applications.
Ray trace algorithm description for the study of pump power absorption in double clad fibers
Show abstract
An algorithm for the analysis of the double clad fiber design is presented. The algorithm developed in the MATLAB
computing language, is based on ray tracing method applied to three-dimensional graphics figures which are composed
of a set of plans. The algorithm can evaluate thousands of ray paths in sequence and its corresponding pump absorption
in each of the elements of the fiber according to the Lambert-Beer law. The beam path is evaluated in 3 dimensions
considering the losses by reflexion and refraction in the faces and within the fiber. Due to its flexibility, the algorithm
can be used to study the ray propagation in single mode or multimode fibers, bending effects in fibers, variable
geometries of the inner clad and the core, and could also be used to study tappers.
Study of an actively Q-switch erbium-doped fiber laser in symmetric configuration
Show abstract
In this paper, we present the results of theoretical and experimental study of the actively Q-switched erbium-doped
fiber laser realized in symmetric configuration. We extend the traveling wave model to this type of fiber lasers and
show that such laser permits one to obtain easily the short giant pulses (17 ns on 3 dB level) with small adjacent subpulses.
Our model accounts all point losses including loss on the fiber splices and other intra-cavity devices and also
the distributed losses such as the active fiber background loss and loss owing to excited state absorption observed in
erbium-doped fibers. We compare the experimental data with the modeling results and reveal their good matching,
once the laser parameters are properly accounted in the model.
Estimation of fiber parameters by using OFRR nonlinear dynamics
Yoh Imai,
Satoshi Yamauchi,
Hirohisa Yokota
Show abstract
In this paper, a new method for measuring the nonlinear refractive index by using the nonlinear dynamics generated in
optical fiber ring resonator (OFRR) is proposed. In OFRRs, input light and circulated light components are added in
succession, and then, result in forming an interference output. The OFRR output exhibits nonlinear dynamics such as a
chaotic state due to the optical Kerr effect, as the input light power increases. In the bifurcation diagram, the output
power indicates peaks in the input power range lower than the bifurcation point at which the output changes from stable
to periodic state. It is found that the input power at the peak shifts, dependent on the nonlinear refractive index. The
nonlinear refractive index can be estimated by applying the measured input power giving the peak point to the numerical
relationship between the input power and the nonlinear refractive index. In experiments the nonlinear refractive index of
the two pure silica core fibers with different cutoff wavelength was estimated as n2=0.97×10-22[m2/V2] and n2=1.06×10-22[m2/V2] which are in good agreement with those reported previously.
Mode-locked all-fiber lasers based on advanced acousto-optic modulators
Show abstract
The development of efficient in-fiber amplitude modulators that operate in the MHz frequency range has enabled some
recent advances in actively mode-locked all-fiber lasers. Our approach is based on the excitation of a standing acoustic
wave along the fiber, which modulates the coupling between modes at twice the frequency of the acoustic wave. Among
the remarkable features of these in-fiber modulators, we mention the high peak power damage, high modulation depth,
broad bandwidth, easy tunability in optical wavelength and low insertion losses. The in-fiber modulation is crucial for
the implementation of all-fiber compact and robust lasers. The experimental characterization of different cavity
configurations as a function of the radio frequency voltage that controls the modulator, the length of the active fiber, the
overall dispersion of the cavity, etc., has led to an improved operation of the lasers: output optical pulses of 34 ps
temporal width, 1.4 W peak power and 4.7 MHz repetition rate, at the emission wavelength of erbium.
Dual wavelength titanium:sapphire laser
Show abstract
On this work we present a Titanium:Sapphire laser with simultaneous dual wavelength operation in the 890 nm region.
Dual wavelength operation is obtained using a novel four stage birefringent filter in which we can control wavelength
separation by tilting one of the filter elements. The laser operates in continuous wave pumped by a 5.5 Watts 532 nm
source producing 100 mW at both wavelengths. We obtained wavelength operation with separation of 2.0 nm to 3.0,
corresponding to frequency separation between 0.8 THz to 1.2 THz. The ultimate goal is the development of a source in
the terahertz (THz) region of the electromagnetic spectrum for medical applications.
Twist-induced birefringence in hexagonal photonic fibers
Show abstract
Photonic crystal optical fibers have much more degrees of freedom concerning the geometries and index contrasts than
step-index fibers; therefore, the theoretical analysis of their performance is usually based on the finite element method.
In this work, taking advantage of the similarities observed for twisted single-mode fibers: standard (SMF-28 and SMF-
28e) and hexagonal photonic fibers, we propose that in regard with polarization performance, photonic fibers can be
described using a simpler model based on classical polarization optics. The main advantages of the matrix model we
propose lie in its accuracy and generality: for each one of the selected wavelengths and input states of polarization, it
allows a precise prediction of the output polarization state. The comparison of the experimental results measured for
standard and photonic fibers with the theoretical model predictions indicates that in both cases, twist induced
birefringence is produced not only by the medium's photoelasticity, but also by the waveguide (cladding/core structure
and asymmetry) modification. In addition, for the photonic fiber, the non-symmetrical response to right and left twist
allowed the identification of an initial twist as part of the residual elliptical birefringence.
Wavelength-switchable fiber laser based on temperature-dependent transmittance of a LPFG
Show abstract
A wavelength-switchable erbium-doped fiber ring laser is demonstrated and reported. The erbium-doped fiber net gain
of the fiber laser is modified by controlled heating of a Long Period Fiber Grating (LPFG) inserted into the laser cavity.
The rejection band of the LPFG is altered in the resonant wavelength and loss according to the exposed temperature and
consequently, the operating wavelength of the fiber laser can be switched from a single wavelength operation at 1563 nm
to a simultaneous operation at 1527 and 1563 nm. The laser system can be used as a temperature fiber sensor as well.
Emergence and degradation of squeezing in resonance fluorescence
Héctor M. Castro-Beltrán,
José R. Herrera-Garza,
Levente Horvath
Show abstract
Using master equation and quantum Monte Carlo wavefunction approaches, we study the circumstances surrounding
the emergence and degradation of the elusive squeezing of fluctuations in two-level atom resonance
fluorescence. For its measurement we suggest conditional homodyne detection (CHD) [G.T. Foster, L.A. Orozco,
H.M. Castro-Beltran, H.J. Carmichael, Phys. Rev. Lett. 85, pp. 3149-3152, 2000], which is nearly independent
of detector efficiencies, which have harmed previous attemps. Squeezing in resonance fluorescence requires a weak
laser, so the average interval between emitted photons is much longer than the regression time to the steady
state; here, the spectrum of the out-of-phase quadrature is a negative peak. In CHD, moderate fields generate
a non-zero third-order correlation in the dipole fluctuations that contaminates squeezing, making the noise non-
Gaussian. If the probability to emit two and even three close photons is still small the additional contribution
is also negative, helping to make the full spectrum a bit larger and easier to measure. Strong driving spreads
the photoemission distribution, which destroys squeezing, and the third order fluctuations become responsible
for the non-classicality of the fluorescence.
Observation of the commutation between bright and dark spatial optical solitons
A. A. Rodríguez-Rosales,
E. Ordoñez,
R. Ortega-Martínez,
et al.
Show abstract
We report a new experimental technique on generation of both dark and bright optical spatial solitons in liquid crystals
doped with organic dyes. In our recent works we have demonstrated that in some liquid crystals (LC's) the effective
nonlinear refraction index (γ) is polarization dependent. Moreover, under certain conditions it is possible to realize
inversion of γ, from γ > 0 to γ < 0, by proper adjustment of incident lightwave polarization. In this work we present
experimental evidence that this LC is capable of supporting both bright and dark spatial solitons. The experimental setup
used for characterization of solitons used two CCD cameras, which allowed us to analyze the longitudinal and transverse
propagation characteristics of solitons in a glass cell containing a LC. It was possible to observe a clear correlation
between the phase and the polarization state of incident light and the characteristic profile of the dark or bright soliton.
The extreme values of the effective nonlinear refraction index were measured to be γ = -4.68 × 10-10 cm2/W (dark spatial
soliton case), and γ = 2.80 × 10-10 cm2/W (bright spatial soliton). The key parameters of spatial solitons were estimated
by using the nonlinear Schrödinger equation.
A simple theoretical model for erbium doped PCF ring lasers design
Show abstract
In this paper a simple theoretical model is presented where the energy conservation principle is used. The model is based
on semi-analytical equations describing the behaviour of an erbium-doped photonic crystal fibre (PCF) inside a ring
laser. These semi-analytical equations allow the characterisation of the erbium-doped PCF. Spectral absorption and
emission coefficients can be determined through the measurement of the gain in the PCF as a function of pump power
attenuation for several fibre lengths by means of a linear fitting. These coefficients are proportional to the erbium
concentration and to the corresponding absorption or emission cross section. So if the concentration is known the erbium
cross sections can be immediately determined.
The model was successfully checked by means of two different home-made erbium doped PCFs. Once the fibres were
characterised the values of the spectral absorption and emission coefficients were used to simulate the behaviour of a
back propagating ring laser made of each fibre. Passive losses of the components in the cavity were previously
calibrated. A good agreement was found between simulated and experimental values of efficiency, pump power
threshold and output laser power for a wide set of experimental situations (several values of the input pump power,
output coupling factor, laser wavelength and fibre length).
Erbium-doped photonic crystal fiber chaotic laser
Show abstract
An erbium-doped photonic crystal fiber laser has been designed, constructed and characterized in order to examine the
feasibility of this kind of devices for secure communications applications based on two identical chaotic lasers. Inclusion
of a tailored photonic crystal fiber as active medium improves considerably the security of the device because it allows
customization of the mode transversal profile, very influential on the laser dynamics and virtually impossible to be
cloned by undesired listeners. The laser design has been facilitated by the combination of characterization procedures
and models developed by us, which allow prediction of the most suitable laser features (losses, length of active fiber,
etc.) to a given purpose (in our case, a laser that emits chaotically for a wide assortment of pump modulation conditions).
The chaotic signals obtained have been characterized by means of topological analysis techniques. The underlying
chaotic attractors found present topological structures belonging to classes of which very scarce experimental results
have been reported. This fact is interesting from the point of view of the study of nonlinear systems and, besides, it is
promising for secure communications: the stranger the signals, the more difficult for an eavesdropper to synthesize
another system with similar dynamics.
Plasmonic core-shell nanoparticle-based thin film solar cells
Show abstract
The enhanced optical absorption in solar cells using nanoscale structure and novel physical effect has received a lot of
attention in recent years. One of the promising methods is to utilize the noble metal nanoparticles with plasmonic effect
for increasing the light absorption, consequently the conversion efficiency of photovoltaic devices. While the bare metal
nanoparticles may suffer from the energy loss introduced by themselves due to the recombination of electro-hole pairs.
Here, we propose to apply the plasmonic metal-dielectric core-shell nano-particles to improve the optical absorption
efficiency of thin film solar cells. It is expected that the metal core could increase the optical absorption of thin film solar
cells due to the filed enhancement effect of localized surface plasmon (LSP), and meanwhile the dielectric shell could
avoid the metal core to become a new recombination center of the light-induced excitons. Further, varying the refractive
index of the dielectric shell could adjust the enhancement region of LSP in a large range to cover the whole wavelength
range of solar cells. Simulations are carried out by means of the finite element method in a three-dimensional model. The
results show that the absorption enhancement up to 110% could be obtained when the active layer of thin film organic
solar cells is 30nm thick. Then, some initial experiments have been done. The Au-citrate core-shell nanoparticles
synthesized by the sodium citrate reduction method are deposited on the solar cells. And the obvious photocurrent
enhancement has been observed.
High-visibility photonic crystal fiber interferometer for ultrasensitive refractometric sensing
Show abstract
A simple and compact photonic crystal fiber (PCF) interferometer that operates in reflection mode is proposed for
refractive index (RI) sensing. The device consists of a ~12mm-long stub of commercially available PCF (LMA-10)
fusion spliced to standard optical fiber (SMF-28). The device reflection spectrum exhibits interference patterns with
fringe contrast up to 40 dB. One of the excited modes in the PCF is sensitive to external RI therefore the device can
be useful for refractrometry. The shift of the interference pattern can be monitored as a function of the external
index. In the operating range, from 1.33 to 1.43, the maximum shift is less than the interferometer period, so there is
no-ambiguity in the measurements. The maximum sensitivity and resolution achieved were 735 nm per RI units and
7×10-5, respectively. Another approach to measure the external RI consists of monitoring the reflection power
located at the quadrature point of the inference pattern in a properly selected wavelength. Consequently the
measuring range is narrower but the resolution is higher, up ~7×10-6, thanks to the high fringe contrast.
Photonic crystal integrated in a waveguide with periodic roughness
A. Mendoza-Suárez,
H. Pérez-Aguilar,
F. Villa-Villa
Show abstract
In this work we consider a waveguide composed of two periodic, perfectly conducting, one-dimensional rough surfaces. This periodic system has a band structure similar in some aspects to a one-dimensional photonic crystal. However our system has some additional interesting features. We calculate the band structure and the reflectivity of a corresponding finite waveguide. We found that the variation of the roughness amplitude and the relative phases allow to control at a certain degree the band structure of the system. Particularly, broad bandgaps can be obtained. The system considered constitutes itself a photonic crystal whose band structure correponds in many ways to a conventional photonic crystal but using just a single material. The key properties of this system are that it really constitutes a waveguide which has integrated a dispositive that acts as a photonic crystal.
Fiber Bragg grating fabrication for the implementation of sensors in the electronics and optoelectronics laboratory at BUAP
Show abstract
Fiber Bragg gratings (FBG) are important optical devices since they have been quite successful not only in the field of
communications but also in sensor systems and optical fiber lasers. In the sensors area they are generally used as
detection elements for different physical parameters such as temperature, strain, flow, etc. In the electronics and
optoelectronics laboratory at Benemérita Universidad Autónoma de Puebla (LEyO-BUAP), there are already
experimental setups of sensors as well as laser systems, where FBGs are fundamental elements for their adequate
performance. However, these FBGs are commercial devices and they present limited characteristics in their transmission
profiles, bandwidth and reflectivity. On the other hand, in some occasions, the delivery time from the fabricant to the
customer is quite long. Therefore, it is important for LEyO to implement a system to fabricate this kind of devices, which
would mean LEyO independence in the technological development. In this work, results of FBGs fabrication based on
the phase mask technique are presented. Such mask is optimized for UV and it has a period of 1060 nm. A Nd:YAG
pulsed laser with a 5 ns pulse length and an energy of 40 mJ was used as the UV source employing the 4th harmonic
generation to obtain a 266 nm wavelength. Ge-doped fiber was used to fabricate the devices.
Gaussian beams to calculate multimode interference in waveguides
Show abstract
In this work, we present an alternative analytical method to describe the multimode interference (MMI) in waveguides. It
is common to use numerical calculation to simulate the MMI, but it usually requires a large amount of computational
resources to obtain the simulation in the corresponding section of the waveguide. Our method is based in the propagation
of multiple Gaussian beams that interfere between them to produce the self-image effect as it appears in the waveguide
MMI phenomena. In this case, we can calculate electromagnetic field distribution at an arbitrary propagation distance
without the need to calculate the field in the entire waveguide section. This method simplifies the characterization of the
MMI based devices as the multiplexor and the called optical fiber beam shaping.
Waveguides by multiple implantations of Ag ion on SiO2 substrates
Show abstract
Optical waveguides have been obtained by silver ion implantation on fused silica substrates. First results of a
methodology oriented to design optical waveguides with silver nanoparticles in a dielectric matrix are presented.
Simulation of ion implantation is based on SRIM code and is correlated with a refractive index increase Δn calculated as
a function of the chemical composition. Effective refractive indices of the propagation modes are determined by prismcoupling
technique.
Polarization entangled photon pair generation in optical fibers with birefringence
Show abstract
Spontaneous four-wave mixing (SFWM) in optical fibers is an important way to generate correlated/entangled photon pairs. When the pulsed pump light passes through the optical fiber, two kinds of SFWM will take place simultaneously. One is scalar scattering processes, in which two annihilated pump photons and generated photon pair are all polarized along the same fiber polarization axis. The other is vector scattering processes, in which two annihilated pump photons are polarized along different fiber polarization axes, either to the two photons of the generated pair. If the fiber has large group birefringence, the intensity of vector scattering processes will be suppressed at the phase matching frequencies of the scalar scattering processes. On the other hand, the walk-off effect of the pump pulse components polarized along the two fiber polarization axes also suppresses the vector scattering processes. Hence, by proper pump polarization and signal/idle frequency selection, photon pairs can be generated only by the two independent scalar scattering processes in optical fibers with birefringence, which provide a simple way to realize polarization entangled photon pair generation. In this paper, related experiments based on the high nonlinearity microstructure fiber (HN-MSF) with group birefringence and polarization maintained dispersion shifted fiber (PM-DSF) are introduced, showing their potential on developing practical quantum light sources.
Polarized light propagation along a helical trajectory
Show abstract
The results of experimental observation of a speckle pattern of light propagating through multimode optical fibers coiled
into spiral are presented. The rotation of the speckle pattern has been observed. It has been shown that the angle of the
speckle pattern rotation (in radians) is numerically equal to the solid angle (in steradians) subtended by the trajectory
tangential vector at the unit sphere.
Theoretical and experimental results of superluminescent fiber optic source
E. F. Pinzón-Escobar,
G. E. Sandoval-Romero
Show abstract
We present a theoretical and experimental work of an erbium-doped fiber optic source operating in the superluminescent
regime. Experimental results for different pump power levels and different fiber length show that the theoretical model
could render useful information for predicting parameters such as total output power, spectral bandwidth and optimum
fiber length for a given pump power to achieve the superluminiscent regime. These types of sources could have direct
application in wavelength multiplexed arrangements of fiber sensors, fiber gyroscopes or in general, in any sensors in
which a broad wavelength and stable light source is required.
Low-cost and biocompatible long-period fiber gratings
Show abstract
In this paper, a low-cost long-period fiber grating (LPFG) induced by a polymeric microstructure is demonstrated.
LPFGs are induced on a tapered optical fiber (TOF) when a periodic micro-grating comes into contact with the thin
region of the fiber. The micro-grating device is made using polydimethylsiloxane (PDMS), an inexpensive, nontoxic and
optically transparent polymer that is extensively used in microfluidics, organic electronics and biotechnological
applications. Soft lithography, along with molds built from thermoplastic polystyrene sheets, makes the fabrication
straightforward and extremely low-cost. Additionally, no precision machining is necessary and the resolution of the
microstructures is limited only by the resolution of the laser printer used for patterning the polystyrene sheets.
The TOF and the micro-grating were dimensionally characterized using optical microscopy and white light
interferometry, respectively. Variations on the optical spectrum due to pressure and temperature were observed and their
magnitudes were similar to those obtained using metallic microstructures. Thus, LPFGs can be made in an inexpensive
and expeditious way using PDMS and TOFs. These polymeric devices can be integrated into microfluidic and other labon-
a-chip systems where biocompatibility is a valuable characteristic.
Analysis of a multipoint sensor based on two Fabry-Perot cavities employing fiber Bragg gratings
Show abstract
A theoretical analysis of a multipoint sensor conformed by two Fabry-Perot cavities, both constructed with two fiber
Bragg gratings (FBG) is presented. Each cavity uses one FGB as reference and the other one as a sensing element. The
signals of the sensors were identified through their fundamental beating frequency (FBF), which is the result of the
interaction of two consecutive modes inside the cavity and its value depends upon the cavity length. The sensor response
was analyzed when there are two or more cavities in the system. In this work there is shown that is possible to determine
the magnitude of several variables from each sensor measuring the FBF signal intensity in the frequency domain using
FFT algorithm. The general conditions of the system operation are discussed. Some preliminary experimental results
about the optimal conditions to be able to distinguish the two sensor signals are presented.
Measurement of group velocity dispersion in optical fiber with a hundreds of meters lengths
Show abstract
In this work an experimental setup that allows evaluating the group velocity dispersion (GVD) in optical
fibers with a hundreds of meters length is presented. The setup was composed by an optical fiber Sagnac
Interferometer, SI. The optical fiber under test and a phase modulator were placed inside of the SI loop. The
main idea is to place asymmetrically the phase modulator inside the SI loop. This means that the fiber length
in both sides of the phase modulator, L1 and L2, satisfy L1<<L2. This unbalance allows evaluating the GVD
due to the fact that contra-propagating beams travel with different propagation constants. With this technique
it was possible to measure GVD with a picosecond temporal resolution without using a fast detector or wide
band-width equipment. Results of GVD measurement performed with the developed algorithm are presented.
CMOS-compatible waveguide-integrated Ge metal-semiconductor-metal photodetectors
Show abstract
We demonstrate Ge metal-semiconductor-metal (MSM) photodetectors monolithically integrated with silicon-oxynitride
(SiOxNy) waveguides. Ge photodetector layer was epitaxially grown by an UHVCVD system and the
waveguide was formed on top of the Ge photodetector by PECVD. The entire process is found to be completely
compatible with the standard CMOS process. Light is evanescently coupled from silicon-oxynitride (SiOxNy)
waveguide to the underlying Ge photodetector, achieving at 2 V a responsivity of 0.33 A/W at 1.55 μm wavelength
and a dark current of 1 μA for a 10 μm long photodetector.
Liquids analysis using back reflection single-mode fiber sensors
Show abstract
We demonstrate a new and simple configuration for measuring physical properties of liquids. With proper data analysis,
the proposed setup can potentially extend its application to chemical analysis and characterization of two-phase fluids.
The fiber sensor is based on the characteristic reflection spectrum obtained from different samples allocated on the tip of
a cleaved single-mode optical fiber. Different tests fluids provide a distinctive reflection spectrum and the physical
properties of the sample can thus be inferred through spectral analysis. Our experiments are based on a single mode
optical fiber dipped into the liquid of interest and a fiber Bragg grating (FBG) interrogator for registering the backreflected
light. We analyze how the pending drops formed on the tip of the fiber generate an interference pattern whose
features depend on the physical properties of the test liquid. The experimental setup is controlled through a virtual
instrument to perform the tests automatically. Each experiment involves data acquisition from the FBG interrogator and
recording images by means of a CCD camera. Image analysis provides information about the geometry of the drop and
fiber positioning is carefully controlled to provide consistent reflection patterns for different experiments with the same
sample. Preliminary results show the correlation between the spectral response and the drop's geometry, which in turn is
directly related to surface tension of the liquid sample. The performance of the proposed configuration is evaluated with
two liquids (glycerin and PDMS polymer) showing the feasibility of this approach for developing a simple fiber optic
liquid analyzer.
New method to characterize Gaussian beams
A. Balbuena Ortega,
M. L. Arroyo Carrasco,
J. A. Dávila Pintle,
et al.
Show abstract
In this work we propose a method to characterize a laser beam based on the Gaussian beam propagation through a lens with
a simple experimental setup that can accurately measure the magnitude and location of the beam waist. The experimental
setup involves a lens and a chopper located on a mechanical mount separated by a distance equal to the focal length of the
lens. To characterize the laser the setup is moved away parallel to the axis of the beam beginning at a distance shorter than
the focal length. A photodetector behind the chopper measure the periodic transmitted intensity and an electrical circuit
generates a square wave whose pulse width is proportional to the beam width at the location of the chopper. The position of
the chopper where the beam width is minimum allow us to calculate the location of the waist, we just need to make a final
measurement of the beam width without the lens to find the magnitude of the waist. All the measurements are fast and only
few are needed to determine accurately the position and magnitude of the beam waist.
Vitrification of photo-curing resins by embedded cantilever and Fizeau interferometer
Gustavo F. Arenas,
Ricardo Duchowicz
Show abstract
We present a method for estimating the relative viscosity and vitrification degree of photo-curing polymeric materials.
Real-time knowing of solidification transition provides important information for many scientific areas. The technique
involves the embedding of one end of a small aluminum cantilever subjected to oscillations of constant amplitude and
frequency, into blends made of unfilled dental resins based on bis-GMA-TEGDMA. These resins were activated for
visible light polymerization by the addition of camphorquinone (CQ) in combination with dimethylamino
ethylmethacrylate (DMAEMA), or ethyl-4-dimethyl aminobenzoate (EDMAB). As the polymerization process
progresses, the embedded end of the beam ceases to be free. Thus, changes in the oscillation amplitude at a given point
near the lower end measured by a Fizeau fiber optic interferometer can be interpreted as a proportional indicator of
solidification in the resin being photocured. Proper measurement of this phenomenon provides a more quantitative
support in the early stages of photo-polymerization. Our results show that the resin passes from liquid to gel, and then to
a vitreous state, in a short time compared with the total photo-curing evolution. As a consequence, after this transition,
polymerization seems to develop mainly by diffusive processes.
Optical characterization of LiBr-H2O using MMI in optical fiber
Show abstract
Heat pumps work with a refrigerant mixture of lithium bromide-water (LiBr-H2O) and the efficiency of the heat pump
may be adjusted depending on the concentration of this mixture. On the basis of the last, in this work an analysis of LiBr
concentration by multimode interference (MMI) effects occurring in a single-mode-multimode-single-mode (SMS) fiber
structure is presented. In the SMS structure the sensitive element consists in a multimode fiber (MMF) section spliced
between two single-mode fibers (SMF) in order to launch light into and recover light from that multimode waveguide.
The multimode fiber (MMF) has no cladding so that its exposed core interacts with different concentrations of LiBr-H2O
which refraction indices are between 1.423 and 1.472. The different refraction indices of the solution covering the
exposed core generate variations in the modes coupling inside the multimode section of the SMS fiber, and therefore, a
different response for each case. SMS fiber structure was designed to generate a first self-image of the input profile at a
1555 nm wavelength. The experimental set up consists of a laser diode operating at 1550 nm as the source of the system,
a photodetector as the transducer of the transmitted intensity and a digital multimeter.
Compression and equalization of arbitrary form pulses for optical fiber applications
Show abstract
In this work we analyze the compression and equalization of pulses in the ps range by using an approach based on the
Radon-Wigner transform (RWT). The whole RWT display is obtained from a generalization of the Fourier transform,
namely the fractional Fourier transform (FRT), by varying the fractional order p from 0 (temporal information) to 1
(spectral information). From the inspection of the RWT the optimum fractional order pC originating the desired
processing condition can be obtained. However, as this signal representation depends on a scale factor which should be
introduced, the value of pC is also affected. This point is here analyzed taking into account the restrictions on the scale
factor which are imposed by the photonic devices involved in an experimental implementation; namely, an amount of
chromatic dispersion and an attainable phase modulation factor. We illustrate the method with some applications which
are of interest in fiber optic links such as second and third order chromatic dispersion compensation and pulse
transmission under a non linear regime. The theoretical model derived from an analytical expression of the FRT is
corroborated with numerical simulations.
Hybrid birefringence and dichromatism in twisted single-mode erbium-doped fibers
Show abstract
In this work we present an experimental evaluation of the twist-induced birefringence changes measured in straight
samples of commercial single-mode erbium-doped fibers. The five commercial samples studied showed a significant
asymmetric response to right and left twists, a result different to that previously measured in standard telecom fibers. We
found similar birefringence responses measured for fibers with different erbium concentrations, developed by the same
manufacturer; while fibers made by different manufacturers presented a non-similar response. Since absorption is an
important characteristic of erbium-doped fibers, we have considered the possible influence of hybrid (linear and circular)
dichroism. Therefore, we calculated the 4×4 Mueller matrix required to predict the induced birefringence taking into
account refractive and absorption anisotropies.
On the influence of the excited state migration on the population gratings amplitude recorded in the transient two wave mixing configuration in Er-doped optical fibers
Show abstract
In this paper we analyze the influence of a spatial migration of the excited states on suppression of the population
gratings recorded in erbium-doped optical fibers (EDF). Such dynamic Bragg gratings are formed via saturation of the
optical transition between the fundamental and the meta-stable states of the active ions and are observed experimentally
via transient two wave mixing (TWM) of the phase-modulated counter-propagating recording waves. The reported
experiments were performed in the spectral range 1492-1568nm, which covers the absorption region of the fundamental
transition 4I15/2→4I13/2 of Er3+ ions. Significantly stronger grating suppression is observed at the central/long-wavelength
regions of the above-mentioned spectral region. A set of similar fibers with essentially different Er3+ ions concentrations
with maximum attenuation of 4, 9, 17 and 35 ± 1 dB/m at 1531 nm was investigated and a clear concentration
dependence of the grating suppression was observed. The TWM measurements are supported by the original
experimental data on the fluorescence depolarization. The observed spectral dependence of the grating reduction factor is
explained using the model of the vacant states limited spatial migration of the excitation among the Er3+ ions.
Phase population gratings recorded in ytterbium doped fiber at 1064 nm
Show abstract
For the first time, the experimental results on spatially uniform photo-induced refractive index changes Δn induced in
ytterbium-doped optical fiber at the wavelength λ= 1064 nm were obtained and directly compared with the efficiency of
the transient two-wave mixing (TWM) via phase population grating. It is shown that the TWM efficiency is in a
reasonably good accordance with the theoretical evaluation based on the Dn measurements. Similar correspondence was
also observed for a significantly weaker spatially uniform saturation of the fiber optical absorption and the TWM
efficiency via absorption type population gratings. In contrast to similar data obtained earlier for erbium doped fibers,
this allows us to assume that spatial diffusion of the excited state among Yb3+ is significantly less efficient than among
Er3+ ions.
Investigation of refractive index distribution in different photonic crystal fiber elements
Show abstract
The paper presents the last data regarding new elements based on photonic crystal fibers such as the low-loss patch
cord with a single mode fiber, the fused coupler, the asymmetric coupler for an active fiber power pump. Their
fundamental optical characteristics including wavelength depending loss as a coupling ratio are presented in this paper
as well as their inner structure (cross section) obtained by SEM. However, the use of SEM for the investigation of the
inner element structure is destructive, thus in the last part of the paper we present the tomographic in-line
determination of geometry and refractive index distribution changes along the investigated photonic structure.
The analysis of different approaches to the photonic crystal fiber data capture with a sufficient optical resolution is
given. The data obtained from the Mach-Zehnder interferometer with different laser sources as well as from the in-line
digital holographic setup are presented and compared. The further enhancement required for the digital in-line
holography is discussed.
Study of upconversion in PCFs with high erbium concentration
Show abstract
We report on a comparison of characterization techniques for high concentration erbium-doped photonic crystal fibres
(PCFs). A highly erbium-doped-silica PCF was fabricated and an amplifier based on the PCF was built. Then,
measurements on the amplifier output optical powers were carried out. To model the amplifier, three different
formalisms were assumed for the Er3+-ion upconversion mechanism and the numerical results were fitted to the
experimental ones. The sets of best-fit parameters are compared and the use of these techniques for active PCF
characterisation is discussed.
An analytical analysis of the nonlinear modes of the coupled silicon-on-insulator waveguides
Show abstract
In the present work we analyze the nonlinear modes of silicon-on-insulator (SOI) nanowires and supermodes of the
coupled SOI waveguides. A generalized analysis of the nonlinear modes of silicon nanowires is given where we have
considered the scalar approximation and its vectorial nature to obtain the analytical profiles. In the scalar approximation,
the analytical analysis of the profiles of the transversal modes is based on the solutions of the Helmholtz equation for
nonlinear periodic media, where we obtain an integral solution for the intensity which is identified with the help of the
elliptic functions. Those modes are characterized by two constants of motion of particular physical significance and in
some approximations the solution could become a soliton or cosenoidal type. Therefore, we describe the solutions on
terms of the movement and integration constants. This is an important result because defines the nature of the solutions,
therein the analysis of the third order polynomials roots of those elliptic functions. The general theoretical model
includes the two-photon absorption (TPA) and the nonlinear Kerr effect implicit in the refraction index.
Tunable dual-wavelength fiber laser based on adjustment of cavity loss by a fiber optic loop mirror
Show abstract
We experimentally demonstrate tunable dual wavelength operation of a fiber laser through adjustment of
cavity loss using a Fiber Optical Loop Mirror (FOLM) with a high-birefringence fiber in the loop. The
reflection adjustment of the FOLM was achieved by temperature control of the Hi-Bi fiber. The spectral
spacing has been tuned from 0.98 to 5.6 nm with a tubable fiber Bragg grating. A temperature change of the
Hi-Bi fiber by 0.1 °C causes a change in the reflectances for the wavelengths.
Theory and simulation of a two coupled-cavities fiber laser
Show abstract
In this work we develop a theoretical model to analyze the response of a two coupled-cavities fiber laser. This
setup operates as an additive pulse mode-locking (APM) laser and its design is based on the combined action
of an active cavity and a passive cavity. The first one is generated with an erbium-doped fiber and two fiber
Bragg gratings (FBGs) as reflective components, while the passive cavity is built with a fiber pigtail being the
corresponding mirrors one of the FBGs and the Fresnel reflection at the fiber end. It is proposed a numerical
model that solves the Non-Linear Schr¨odinger Equation (NLSE) by using the Split-Step Method (SSM) together
with the T-Matrix Method (TMM) to calculate the coupling factor on each reflective component. The main
parameters are: the group velocity dispersion (GVD), the self-phase modulation (SPM), the gain and/or loss
factors of the fibers including self-saturation effect and the reflectivity and dispersion characteristics of each
FBG. The dependence of both, temporal and frequency behaviour of the generated emission with the several
involved setup parameters are analyzed. The numerical results produced by applying the theoretical model are
compared with previously obtained experimental results, and a good agreement between them is observed.
Soda-zinc-aluminosilicate glasses doped with Tb3+, Ce3+ and Sm3+ for frequency conversion and white light generation
Show abstract
Sodium-zinc-aluminosilicate (NaZAS) glasses doped with single or multiple rare earth ions (Ce3+, Tb3+, Sm3+) were
synthesized, and their characteristics investigated by m-line spectroscopy, absorption and luminescence spectroscopy,
and micro-Raman spectroscopy. Blue-white light, with x = 0.24 and y = 0.24 CIE chromaticity coordinates, was obtained
for the Tb3+ singly-doped glass excited at 351 nm. In NaZAS glasses co-doped with Ce3+ and Tb3+ it was possible to
observe a non-radiative energy transfer from Ce3+ to Tb3+ ions upon 320 nm excitation; the Ce3+→Tb3+ energy transfer
microscopic parameter and efficiency were obtained from the analysis of the cerium emission decay curve. Different
concentrations of Ce3+ and Tb3+ ions in the same glass host give rise to blue and blue-green emissions, with different CIE
coordinates. Optical waveguides were also produced in the samples by means of Ag+-Na+ ion exchange process, and
characterized.
Development and analysis of a simple tunable erbium ring laser
Show abstract
An all-fiber tunable erbium ring laser operating in the range of 1520-1570 nm was developed. The ring configuration
employs a Fabry-Perot tunable filter with a Free Spectral Range (FSR) of 60nm and a bandwidth of 60pm. Several
devices developed with different lengths of doped fiber were analyzed showing a trade-off between spectral flatness and
output power. A simple rate equation model was further implemented to analyze the laser properties as its temporal
behavior and the spectral dependence of the laser output. Theoretical and experimental results agree.
Measurement of gasoline adulteration using optical fiber sensor
Show abstract
This paper presents the application of a fiber optic sensor based on bifurcated fiber bundles; in the bifurcated design,
separate fibers carry the excitation and emission radiation. The physics principle is simple, the fraction of light
transmitted between the receive elements in the bundle and the transmit elements in the bundles depends of the light
wave passes through the gasoline; three fuel-adulterant mixtures in different proportions by volume were prepared and
individually tested. The high sensitivity of laser, and the versatility of fiber-optic technology and experiment proved that
the system has simple construct and high sensitivity during absorption on a transition process.
Spectroscopic detection of metals ions using a novel selective sensor
Show abstract
Colorimetric chemosensors are simple, economical and practical optical approach for detecting toxic metal ions (Hg2+,
Pb2+, Ni2+, etc.) in the environment. In this work, we present a simple but highly specific organic compound 4-chloro-2-((E)-((E)-3-(4-(dimethylamino)phenyl)allylidene)amino)phenol (L1) that acts as a colorimetric sensor for divalent metal
ions in H2O. The mechanism of the interaction between L1 and various metal-ions has been established by UV-vis
absorption and emission spectroscopic experiments that indicate favorable coordination of metal ions with L1 in
different solvents. Experimental results indicate that the shape of the electronic transition band of L1 (receptor
compound) changed after the interaction with divalent metal-ions, such as Hg2+, Pb2+, Mn2+, Co2+, Cu2+, and Ni2+ in
aqueous solution. We found that L1 have a considerable selectivity for Ni2+ ions, even in presence of other metals ions
when mixtures of DMSO/H2O as are used as solvents. L1, which has been targeted for sensing transition metal ions,
exhibits binding-induced color changes from yellow to pink observed even by the naked eye in presence of Ni2+ ions.
Characterization of photon counter devices for biomedical applications
Show abstract
In this work we characterized several state-of-the-art high sensitivity optical detectors. We compared
avalanche photo diode devices (APD) with multi-pixel photon counting devices (MPPC) in several
characteristics such as detection efficiency and response times. We then discussed some of the results.
Higher-order dispersion terms of a photonic crystal fiber with hexagonal holes
Show abstract
In the modeling of supercontinuum generation in photonic crystal fibers by ultrashort pulses, the knowledge of the
higher-order dispersion terms of the fiber are necessary to achieve a good approximation between the simulated and
experimental spectra. However, these parameters are usually not provided by the manufacturer. In this work, we present
the numerical estimation of the higher-order dispersion terms for a nonlinear photonic crystal fiber with hexagonal holes.
For the simulation, we chose a commercial fiber with a high nonlinear response (Blazephotonics NL-2.4-8). The fiber
was designed with a small core diameter of 2.4 μm and a triangular pattern of air holes in the cladding with a pitch of
2.9 μm. Through the free software, MIT Photonic Bands, the structure of the fiber was modeled and the effective
refractive index, as well as the dispersion terms curves are estimated. From our results, the zero-dispersion wavelength of
the fiber resulted to be of 800 nm and at this wavelength, the higher-order dispersion terms were: β2=0, β3=0.05 ps3/km,
β4=-7.03×10-5 ps4/km, β5=1.4×10-7 ps5/km, β6=-4.163×10-10 ps6/km, β7=1.118×10-12 ps7/km. The zero-dispersion
wavelength and the dispersion slope estimated at this wavelength agree with the values reported by the manufacturer.
Photonic second-order duty-cycle modulator
Show abstract
The delta sigma modulator (DSM) is a device which transforms the amplitude information of an analog input signal
to the duty cycle and frequency of a binary output. This device, typically employed in oversampled analog-to-digital
converters, is based on a feedback loop which includes at least one integrator and one quantizer in the forward path. In
this paper, a novel photonic second-order DSM is proposed and experimentally demonstrated. The system is composed
of two inverted leaky integrator and one electro-optic quantizer. The maximum input frequency is around 2 MHz,
limited by the fiber length of the accumulator and feedback loops, and the quantizer rise/fall times. The system is
characterized at different input frequencies and waveforms (sinusoidal and saw tooth) to analyze the modulator
performance and linearity. The binary output is acquired, processed and demodulated using a personal computer, in
order to reconstruct the input analog signal. The reported fiber-optic DSM is very promising for future integration
increasing the operation frequency up to GHz range.
Nonlinear pulse propagation inside coupled silicon nanowires
Show abstract
In this work we describe the nonlinear propagation of optical pulses through an array of silicon nanowires made with
the silicon-on-insulator technology. A generalized analysis of the nonlinear coupled system is given where we have
considered the vector nature of optical modes and the effects of two-photon absorption on various nonlinear processes.
The general theoretical model includes not only the effects of free-carrier absorption and free-carrier dispersion but also
linear and nonlinear losses, and it extends previous vector nonlinear models to the case where coupling of supermodes of
a waveguide array occurs in silicon waveguides. Analytical solutions are provided for the coupled-mode equations in
some cases in which the density of the free carrier is relatively low, and dispersive effects are relatively weak, assuming
that the nonlinear effects do not affect the waveguide modes significantly. The impact of two-photon absorption and
free-carriers effect on the properties of the nonlinear coupling effects is studied in detail together with the evolution of
optical power inside an array of silicon nanowires.
Inhomogeneous fields for surface plasmon excitation
Show abstract
Point sources of polarized light generate inhomogeneous fields at the surface of a metallic slab
localized at its vicinity. It is found that the associated k-spectrum contains wave vectors larger than
those corresponding to free oscillations. Consequently evanescent fields are available and surface
plasmons can be excited. With FDTD calculations we prove in detail this effect using a point source
of cylindrical symmetry placed near a silver film. In addition, the interaction of the cylindrical wave
and the metallic surface is analytically described by writing the incident wave in terms of a plane
wave basis. Images of the surface plasmon excited by this source and the field distribution in the
vicinity of the surface are shown.
Beam modulated fanning in a crystal BaTiO3
Show abstract
Communication systems require devices that allow rapid distribution of signals to multiple users. We presented a
proposal for a demultiplexer based on the fanning effect. Beam fanning is a process similar to two-beam coupling, except
in this case, in where only one beam is incident on the material and its energy is transferred into scattered light. As a
result of the energy transfer, scattered light is amplified, and a "fan" is observed. Since energy transfer direction can be
changed by switching the polarity of the applied electric field, beam fanning effect can be maximized or minimized on
depending of the polarity. We propose an optical router method with the photorefractive beam-fanning. In this method, a
Gaussian modulated beam passing through a photorefractive BaTiO3 crystals spreads into a some beams that arises from
stimulated scattering. This fanning can be controlled changing the polarization of the beam or the incident angle toward
the crystal. Each scattered beam maintains the input modulated frequency in a wide range. Our results show the possible
application of the fanning effect as an optoelectronic demultiplexer.
Raman gain calculation by Raman threshold study in telecom fibers
Show abstract
A simple experimental configuration for measurement of the Raman gain coefficient is demonstrated. The Raman
threshold condition plays a role important to calculate the critical power and the Raman gain coefficient. Analysis of the
Raman threshold for second Stokes shows that the Raman gain coefficient scales with the inverse of the pump
wavelength and the fiber attenuation, the obtained values are approximate to several quantities previously reported. With
those physical properties the single pass evolution of pump and Stokes beams equations are simulated for different fiber
lengths and several coupled pump powers. The numerical simulations show that the fibers losses and the numerical
aperture play a predominant role in the Stokes generation. These results allow designing optical fibers efficient and/or
poor in the Stimulated Raman scattering generation.
Plasmon excitation using a dielectric slab with diffusion type photorefractive nonlinearity
Show abstract
We investigated numerically the TM electric field solutions of a dielectric slab formed by a photorefractive crystal with
diffusion-type nonlinearity and limited by two metallic films. This study allows us the analysis of nonlinear surface
optical waves as nonlinear solutions of the photorefractive crystal slab. Additionally, we analyzed the influence of these
nonlinear solutions to excite surface plasmon-polariton waves at the metallic interfaces. In this case, the coupling
between plasmons and nonlinear solutions it is possible because only TM electromagnetic waves are supported by a
metal-dielectric planar waveguide. Here, we solved the vectorial and nonlinear wave equation using an iterative method
based in self-autoconsistency. With this algorithm, the coupling between the waveguide modes and the surface plasmon-polariton
waves are systematically investigated. The results obtained in this work are reproducible and contributes with
new information for the design of tunable plasmonic devices based in nonlinear photorefractive crystals.
Multimode interference effects in optical fiber for pressure sensing applications
Show abstract
Applications of Multimode Interference (MMI) effects in optical devices have been increased today due their excellent
properties and easy fabrication. Incorporation of these effects in optical fiber has been achieved through a single-mode -
multimode - single-mode (SMS) fiber structure showing high sensitivity to bending-loss phenomenon. The latter has
been efficiently implemented in pressure sensing application such as is presented in this work. Basically, the SMS
structure is embedded in a pressure-sensitive membrane to convert pressure in a mechanical displacement resulting in an
attenuation of the transmitted intensity proportionally to the applied pressure. Under this configuration, an all-fiber
pressure sensor with high sensitivity and repeatability is obtained into a pressure range from -13 psi to +13 psi. The max
pressure range can be varied to 140 psi with our configuration when the membrane thickness is changed. Important
features of the proposed all-fiber MMI pressure sensor are its easy-fabrication and low-cost since an inexpensive
instrumentation is required.
Influence of geometry of waveguide arrays to get discrete solitons
A. Vergara Betancourt,
G. Mendoza González,
L. C. Gómez Pavón,
et al.
Show abstract
Based on the numerical experiment techniques, we addressed this work to the study of the physical
parameters, which allow the discrete soliton formation and propagation in two dimensional
waveguide arrays of different geometries. The mathematical model is based on the two
dimensional nonlinear Schrödinger equation, and from the boundary conditions we are able to
conclude that the array geometry plays an important role in the energy demands for the discrete
soliton formation and propagation over distances of hundreds of diffraction lengths. Furthermore,
our results are consistent even in the case when we take into account coupling of higher orders.
Quasi-continuous wave OPO based on periodically poled lithium tantalate
Show abstract
We present a singly resonant optical parametric oscillator based on periodically poled lithium tantalate emitting
on quasi-continuous wave mode (~400ns) from 1.48 to 1.6μm with power threshold less than 40W of peak power. We
have obtained ~50% of optical to optical conversion efficiency from pump wavelength to other wavelengths.
Measurement of curvature and temperature using multimode interference devices
Show abstract
In this paper we propose the fabrication, implementation, and testing of a novel fiber optic sensor based on Multimode
Interference (MMI) effects for independent measurement of curvature and temperature. The development of fiber based
MMI devices is relatively new and since they exhibit a band-pass filter response they can be used in different
applications. The operating mechanism of our sensor is based on the self-imaging phenomena that occur in multimode
fibers (MMF), which is related to the interference of the propagating modes and their accumulated phase. We
demonstrate that the peak wavelength shifts with temperature variations as a result of changes in the accumulated phase
through thermo-optics effects, while the intensity of the peak wavelength is reduced as the curvature increases since we
start to loss higher order modes. In this way both measurements are obtained independently with a single fiber device.
Compared to other fiber-optic sensors, our sensor features an extremely simple structure and fabrication process, and
hence cost effectiveness.
Highly efficient photorefractive polymers doped with cyano nonlinear chromophores
Show abstract
In this work we report new highly efficient organic photorefractive polymers based on aryl-cyano non-linear
chromophores [(4-(diethylamino)-2-hydroxybenzylideneamino]benzonitrile (CN-C-OH) and [4-(diethylamino)
benzylideneamino]benzonitrile (CN-S-OH). The PR polymer blends are composed by the photoconductor poly
(9-vinylcarbazole) and plasticizer 9-ethylcarbazole PVK:ECZ matrix, as well as the sensitizer fullerene C60.
Holographic experiments in a tilted four wave mixing (FWM) and two beam coupling (TBC) geometry were
carried out by using a 10 mW He-Ne laser (633 nm). The experiments were performed at room temperature to
measure the electric field steady-state diffraction efficiency dependence of the PR composites. High diffraction
efficiency as high as 90 % was observed for polymers based on CN-C-OH at 25 wt. % doping level and an
external applied electric field around 56 V/μm. The μβ product was also measured by EFISH technique for
compounds CN-C-OH and CN-S-OH, results showed that CN-C-OH present a value 3.5 times higher than CN-S-
OH, which is supported by a theoretical prediction. Demonstration of fast reversible holographic imaging (~0.5
s) by using these highly efficient organic photorefractive polymers based on CN-C-OH and CN-S-OH is
presented.
Study of laser channel waveguides in Nd:YAG crystals obtained by proton implantation
Show abstract
In this work a study of the effects on the optical properties of channel waveguides in Nd:YAG crystals fabricated with
different proton implantations doses is presented. The channel structure was achieved by using an electroformed mask
with openings through which the protons were implanted. The optical properties studied included microphotographs, the
transversal modal distribution at visible wavelengths, the photoluminescence spectra and the laser emission. The laser
performance of the waveguides was obtained in a resonant cavity configuration with mirrors held onto the polished end
faces of the waveguides.
Theoretical Optics
Exact modeling of propagation of partially coherent optical fields
Show abstract
Due to analytical and numerical difficulties, the propagation of optical fields in any state of spatial coherence is
conventionally computed through severe approximations; Fresnel-Fraunhofer approach is one of the most widely used.
These approximations provide in many cases a rough knowledge of the actual light behavior as it propagates. However,
the complexity of the actual developments requires non-approximated procedures capable of modeling the propagation
of optical fields in any state of spatial coherence. The proposed model bases on expressing the classical cross-spectral
density in center-difference coordinates, which allows for its exact calculation in very practical cases. The results reveal
unaware behavior of light as it propagates, and equal those obtained with the conventional computation approaches as
approached to the Fresnel-Fraunhofer regime. Light behavior close to the diffraction transmittances can also be learned
with the aid of the proposed modeling tool.
Vector-electromagnetic scattering from metal surfaces using the infinite-slope Kirchhoff approximation
N. C. Bruce
Show abstract
One of the most popular methods for calculating the scattering of light from rough surfaces is the Kirchhoff
approximation. A recent modification of the Kirchhoff approximation allows calculation of the scattering of
electromagnetic radiation from rough surfaces with very high, or even infinite, slopes, which occurs frequently in, for
example, imaging or testing of printed circuits or remote sensing applications. The modification involves a simple
change in the way the surface normal is described which removes the explicit dependence of the resulting integral
equations on the surface slope, and changing the sampling of the surface, removing the requirement of small slopes for
application of the method. In this paper we present the application of the method to vector electromagnetic scattering,
using the Stratton-Chu equation, from 2D rough metallic surfaces with infinite slope. The single and double scatter
contributions to the total scattered intensity are calculated numerically with this new formulation. Geometrical
shadowing is included by using ray tracing directly on the surface. The theoretical basis and preliminary numerical
results of the application of this method to vector electromagnetic scattering from simple rough metallic surfaces (plane
surfaces with single grooves or with a small number of identical grooves) with infinitely sloped structure are presented.
Reflected wave atypical phase change at a boundary
Show abstract
According to Fresnel formulae, at normal incidence on an abrupt interface, the reflected wave has a phase
difference of zero or π, if the second medium has a lower or larger refractive index than the first. However, what
happens if the refractive indices of two media are the same at the interface but the derivative of the refractive
index varies abruptly? Since the two media are not homogeneous because the refractive index derivative is finite,
the problem cannot be tackled with the Fresnel formalism. In order to deal with this problem the amplitude and
phase representation of plane electromagnetic waves is used. An invariant is obtained that permits the decoupling
of the amplitude and phase equations, both of which, are nonlinear. The amplitude equation is then solved
numerically. No approximations are made regarding how slow or fast refractive index varies compared to the
wavelength. Interpretation of the amplitude equation solutions reveal that surfaces where any of the derivatives
of the refractive index profile is discontinuous, do enhance reflection. At normal incidence, the reflected wave
thus generated will have a phase difference that may be a multiple of π/2, apparently contradicting the Fresnel
equations.
Alternative coherent-mode representation of a planar electromagnetic source
Show abstract
Recently we have reported on the alternative coherent-mode representation of a scalar optical source which does not
involve the solution of the Fredholm integral equation with the source cross-spectral density as a kernel but is based on
results of usual radiometric measurements. Here we generalize such a representation for the case of vector
electromagnetic source. The technique of constructing the proposed representation is illustrated with results of
mathematical simulation.
Coherence and polarization control using nematic 90-degree-twist liquid crystal spatial light modulators
Show abstract
An experimental technique for controlling the statistical properties of a primary source by means of nematic 90°-twist
liquid-crystal spatial light modulators (LC-SLMs) is proposed. The modulation of coherence and polarization is achieved
through computer generated random signals applied to LC-SLMs placed at the opposite arms of an interferometric setup.
Experimental results obtained by using Holoeye LC2002 modulators show the efficiency of the proposed technique.
Antenna of adjustable bandwidth based on a pentagonal array
Show abstract
Antenna characteristics are chosen according to the features determined by the systems where they will be used. While
some systems require a very narrow bandwidth, others may operate with a much wider bandwidth. Some techniques used
for increasing the bandwidth of a given antenna have considered mechanical adjustment of the air layer thickness, with
the consequent change on the effective permittivity and performance. Some other systems consider a suitable choice of
feeding techniques and impedance matching network. However, approaches for reducing the bandwidth have not
received the same level of attention. Narrow bandwidth antennas are of particular interest in security and surveillance
systems. In this work we present a technique, based on the design of a pentagonal antenna array, which allows for
adjusting the bandwidth in either direction. The array is formed by an inner patch designed at the desired operating
frequency of the system and a gap coupled external ring centered at a different frequency (lower or very near the
operating frequency), which determines the potential bandwidth increment or decrement. The feed point is located on the
inner patch. As a proof-of-concept, this work offers a tuning range that goes from -40% of the center frequency up to
+50% of the center operating frequency of the patch antenna. The single patch antenna of this work was designed and
simulated at an operating frequency of 4.9 GHz on RT/Duroid 5880.
Chain-like beams with phase singularity
Show abstract
The investigation of the first order Bessel beam diffraction on a binary amplitude diffraction mask with two open zones
has been performed. It has been shown by computer modeling and experimentally that the structure of the beam intensity
distribution along the propagation axis resembles a chain-like beams structure, but a dark hole can be observed along the
propagation axis in the center of the beam. The interference pattern of the beam under investigation and Gauss beam has
demonstrated the phase singularity presence. The transverse intensity distribution of the beam has shown ring structure
with periodically changing intensity.
Influence of polarization on speckle patterns in the Laser MegaJoule configuration
Show abstract
This paper investigates hot spot characteristics generated by the superimposition of multiple laser beams in the Laser
MegaJoule configuration. First, properties of speckle statistics are studied in the context of the superimposition of several
laser beams. The case of a single quadruplet is studied. Values of the speckle width and of the speckle length as well as
of the abundance of the speckles are compared to the results given by numerical simulations. Application to the speckle
patterns generated in the Laser MegaJoule configuration in the zone where all the beams overlap is then presented. The
case of three different polarizations is investigated: P polarization, S polarization and the case of Double Polarization
smoothing (DPS). It is found that the sizes of the speckles and their abundance depend on the choice of the polarization
and that DPS seems to be the best option.
Beam mapping on the orbital Poincaré sphere
Show abstract
Representation of two-dimensional optical signals on the orbital angular Poincaré sphere is useful for beam
analysis, synthesis and comparison. This mapping is based on the measurement of the second-order moments,
which are widely used for beam characterization. It is well known that two second-order moments invariants
allow dividing two-dimensional signals into two classes: isotropic and anisotropic. Using the modified Iwasawa
decomposition of the ray transformationmatrix and bringing the second-order moments matrix to its diagonalized
form, we are able to associate the anisotropic signal with a certain point on the sphere. The latitude of this point
describes the vorticity of the signal, while its longitude corresponds to the orientation of the beam's principal
axes. Apart from that, the beam's scaling and its curvature can be defined. Before beam comparison, it is thus
appropriate to perform first its normalization and mapping on the Poincaré sphere. There are many very different
beams associated with the same point and therefore this procedure makes sense for fine analysis of beams whose
intensity distributions have similar forms. Moreover, every point on the sphere is associated with an orthonormal
set of Hermite-Laguerre-Gaussian modes, which can be used for the corresponding beam decomposition that is
important for its synthesis and analysis. The developed algorithm for the beam mapping is demonstrated on
several examples.
Finite optical Hamiltonian systems
Kurt Bernardo Wolf,
Natig M. Atakishiyev,
Luis Edgar Vincent,
et al.
Show abstract
In this essay we finitely quantize the Hamiltonian system of geometric optics to a finite system that is also Hamiltonian,
but where signals are described by complex N-vectors, which are subject to unitary transformations that
form the group U(N). This group can be decomposed into U(2)-paraxial and aberration transformations. Proper
irreducible representation bases are thus provided by quantum angular momentum theory. For one-dimensional
systems we have waveguide models. For two-dimensional systems we can have Cartesian or polar sensor arrays,
where digital images are subject to unitary rotation, gyration or asymmetric Fourier transformations, as well as
a unitary map between the two arrays.
Mie scattering of high numerical aperture fields
Nicole J. Moore,
Miguel A. Alonso
Show abstract
Recently, we proposed several complete orthonormal bases to increase the efficiency of modeling directional, high
numerical aperture fields for both the scalar and electromagnetic cases, based on the idea of imaginary focus
displacements. Their elements, which can be thought of as nonparaxial analogs of Laguerre-Gauss beams, are
analytic solutions to the wave equation in free space and can be optimized for the particular angular spread (NA)
using a single parameter corresponding to the imaginary displacement. The scattering of these basis elements
off spherical particles can be calculated analytically, as can also the resulting forces and torques exerted on
the particle by any linear combination of these fields. Applications involving both fully coherent and partially
coherent fields are discussed.
Light propagation through thin films: the amplitude and phase representation
Ruth Diamant
Show abstract
The amplitude and phase representation of classic electromagnetic waves is used to model light propagating
through a stratified medium, with a continuous refractive index profile. This medium is assumed to be isotropic,
non magnetic, electrically neutral, transparent, dielectric, with a linear response, but letting the electric permittivity
vary along the z direction. No approximations regarding a slowly or strongly varying refractive index,
compared to the wavelength, are made. This is particularly convenient when the refractive index varies on a wavelength
scale. The case of a thin film at normal incidence is studied for various thicknesses and interface ranges.
The corresponding nonlinear amplitude differential equation is numerically solved. The amplitude oscillations
are construed in terms of counter-propagating waves and the film's reflectivity is evaluated.
Omnidirectional reflector in a ternary metallo-dielectric structure
Show abstract
We discuss the complex dispersion relation of a one dimensional metallo-dielectric photonic crystal, produced by a
dielectric photonic crystal with extremely thin metallic inserts with the same periodicity. We have carried out the
analytical and numerical analysis. Also, we show a method to avoid the problem of solving the complicated system of
transcendental equations of the dispersion relation that was proposed previously for us and we extended it to the oblique
incidence, i.e., for calculating transversal electric and magnetic modes. Moreover, we demonstrated a metallic band gap
not only at the bottom but also at high frequencies.
Speckle contrast measurement with low light levels and imperfect laser illumination
Show abstract
The contrast of a speckle pattern, defined as the ratio of the standard deviation of intensity to the mean intensity, is an
important parameter that can yield useful information in vibration analysis, and surface roughness measurement. It is
also of inherent interest in the measurement of scattering by coherent X-rays. Under some circumstances, the light levels
at which contrast measurements must be made are low, and the measurement of speckle fluctuations is complicated by
the presence of noise associated with discrete detected photoevents. In addition, the measurements are made over a finite
integration time and a finite integration area, so it is the contrast of the integrated intensity that is of interest. The goal of
this paper is to explore the effects of both photoevent noise and source fluctuations on the measurement of speckle contrast.
Thus in themost general case, there are three sources of randomness, source fluctuations, random scattering and photoevent
fluctuations. Partial motivation for the investigation is understanding the photoevent statistics and speckle count contrast
for synchrotron and fee-electron laser sources.
Partial coherence and polarization in electromagnetic interference
Show abstract
While the theories of the optical coherence of scalar fields and the polarization of beam fields are well established, a
general theory for the coherence and polarization of true electromagnetic fields appearsmore subtle. With random
vector fields coherence may reside among any or all of the electric-field components, leading to a modulation
of the optical intensity or the polarization state, or both, on two-beam interference. We discuss the recent
formulations of both the polarization and the coherence, and we show that the electromagnetic degree of coherence
is characterized by the modulation of all the four Stokes parameters (representing intensity and polarization state)
in a two-pinhole Young's setup. This also leads to a new experimental interpretation for the degree polarization
of a random electromagnetic beam. Certain important results pertaining to electromagnetic coherence, which
are fully analogous to their scalar counterparts, are emphasized.
Analytical description of band gaps in a ternary metallo-dielectric stack
Show abstract
Metallo Dielectric Photonic Crystals formed by same periodicity metallic inserts in a Dielectric Photonic Crystal show
three kind of band gaps, those at the well know dielectric band gap, the ones attributed to the absorption of metal to low
frequencies and a new class of metallic bandgaps. Numerical studies have confirmed that while the dielectric band gap
width is basically described by the refraction index contrast, the width of the metallic band is described by the thickness
of the metal inserts. In this work we carry on the corresponding analytical analysis of both band gaps for this one
dimensional ternary dielectric-dielectric-metal structure. The stack that we are proposing is a quarter-wave for the
dielectrics and the thickness of the metallic layers is changed as a free parameter. Using standard transfer matrix
formalism, we find a closed form of the dispersion relation and from it; we have analytically demonstrated the formation
and width of the dielectric band gap and its metallic perturbation, as well as those of the additional metallic band gap.
Generation of a spiral wave using amplitude masks
Show abstract
Optical beams of Bessel-type whose transverse intensity profile remains unchanged under free-space propagation
are called nondiffracting beams. Experimentally, Durnin used an annular slit on the focal plane of a convergent lens
to generate a Bessel beam. However, this configuration is only one of many that can be used to generate
nondiffracting beams. The method can be modified in order to generate a required phase distribution in the beam. In
this work, we propose a simple and effective method to generate spiral beams whose intensity remains invariant
during propagation using amplitude masks. Laser beams with spiral phase, i.e., vortex beams have attracted great
interest because of their possible use in different applications for areas ranging from laser technologies, medicine,
and microbiology to the production of light tweezers and optical traps. We present a study of spiral structures
generated by the interference between two incomplete annular beams.
Influence of the mechanical stress and heat parameters into the transmittance function of the integrals of the diffraction phenomena
Show abstract
For the diffraction equations for the exact and convolutions Fourier's integrals, the parameters related with mechanical
stress and heat are introduced into the mathematical function of the transmittance t0(x0,y0). Taking into account the new
transmittance equation, a new set of equations for the exact and convolution Fourier's integrals have been derived. The
only restriction for the analysis done is that for the apertures under study, they are only on a plane. An example af an
experiment where a diffraction aperture suffers of a mechanical stress is shown.
On nonplanar radon transforms for weakly absorbing gradient-index media
Show abstract
In this work we explore extensions of the well-known tomographic imaging process to gradient-index media within
the geometrical optics regime. We propose a generalized Radon transform that relates a linear weak-absorption
profile to the change of intensity due to a varying wavefront.
Optical resonators and dynamic maps
Show abstract
In this article the dynamical behavior of a beam within a ring phase-conjugated resonator is modeled using two
dimensional iterative maps. In particular it is explicitly shown how the difference equations of the Duffing and
Tinkerbell maps can be used to describe the dynamic behavior of what we call Duffing and Tinkerbell beams i.e. beams
that behave according to the Duffing and Tinkerbell maps. The matrix of a map generating device is found in terms of
the maps parameters, the state variables and the resonator parameters. The mathematical characteristics of an optical
device in an optical cavity are stated so that a chaotic map is obtained as the dynamics for the ray beams.
Photonic crystal slab with layered elements
Show abstract
Abstract We introduce the simulation of a photonic crystal slab with a square lattice, whose basis elements are layered cylinders of an averaged refractive index <n>. We compare it with a similar photonic crystal with a basis of the same size and a refractive index matching to the average of the layered ones. Even when this is such a simple system with internal structure, we have found an interesting phenomenology: an increase in band gaps, flattening of the bands, degeneracy nodes, etc. We also introduce additional methods to fine tuning the design and analyze the inclusion of a plain cylinder defect within the slab.
Stratified media: nonlinear ODE is better
Show abstract
Propagation of light in stratified media is described with Maxwell's partial differential equations (PDE). Separation of variables allow to decouple the linear PDE's to obtain second order non autonomous linear ODEs for the electric and magnetic fields. In the last decades, the problem has been tackled with matrices whose elements are linearly independent solutions of the fields.
In our approach, although counter-intuitive, the linear differential equations are transformed into a non-linear ODE. To this end, the field is written in terms of amplitude and phase variables. An Ermakov invariant then permits the decoupling of the amplitude and phase nonlinear equations. The amplitude or Milne nonlinear equation is then solved numerically. This method has important advantages: i) initial or final conditions are easily imposed, ii) important physical quantities such as the reflectivity are readily obtained, iii) no further approximations have to be made iv) complex profiles can be modeled with arbitrary degree of precision. The abrupt and adiabatic limits are obtained but most importantly, intermediate more realistic cases can also be tackled, for example, adsorption between thin film layers. Novel effects are addressed such as enhanced reflectivity at derivative discontinuities where the refractive index is continuous.
Generalized phase space representations in classical optics
Show abstract
We give a prescription for defining generalizations of the Wigner function that allow extending the property
of conservation along paths to a wider range of problems, including nonparaxial field propagation and pulse
propagation within general transparent dispersive media.
Classical modelling of the fourth-order spatial coherence state of scalar wave-fields
Show abstract
The fourth-order spatial coherence state of wave-fields is described in the framework of the classical wave picture, by
means on the four-order spatial coherence wavelets. This strategy suggests that the fourth-order spatial coherence state of
light can be modelled in terms of three layers of point sources in order to increase the performance of numerical
algorithms. The model is illustrated by applying it to the Hanbury-Brown & Twiss effect.
Resumming divergent series in nonparaxial optics
Show abstract
We show that the terms of a Lax series, commonly used to evaluate propagated optical fields in nonparaxial conditions, present a factorially divergent asymptotic behavior in the case of highly nonparaxial beams, under rather general conditions.
This allows some resummation algorithms, such as the Weniger transformation, to be used in order for the evaluation of the propagated field to be successfully performed starting from the terms of the divergent Lax series.
Examples are presented, concerning cases for which the terms of the Lax series can be evaluated explicitly.
Angular momenta and spin-orbit interaction for nonparaxial beams
Show abstract
It is well known that, for any monochromatic field, the spatial extent of the focus has a lower bound dependent
on the field's directional spread. The influence that the orbital angular momentum and, for vector fields, the
(spin) angular momentum due to polarization have on this lower bound are studied here for fields not constrained
by the paraxial approximation. A ray-optical interpretation of the effect of orbital and spin angular momentum
on the spatial spread is provided for the case of Bessel beams.
Transverse energy flux estimation in optical vortices by single-slit diffraction
Show abstract
We propose a simple technique for the estimation of the local inclination angle of the helical wave fronts, and thus
the direction of the transverse energy flux, in beams with embedded optical vortices. It is based on the analysis
of the evolution on propagation of the asymmetric diffraction pattern produced by a single-slit aperture.
Optical Engineering
Performance measures for pattern recognition in a wavelet joint transform correlator
G. Mestre,
C. Torres
Show abstract
The present paper shows the results of the implementation of a correlation Digital processed Joint Wavelets for gray
level images target recognition applications. The aim is to study and characterize the different families of twodimensional
wavelets that are available and build a system of recognition of images it becomes operational, flexible and
reliable. The resulting methodology of this study becomes a useful tool to implement in the future, in which the
evolution of technology will provide greater reliability and algorithms will allow the design of correlation more compact,
fast and versatile with multiple applications. The correlation was tested in image recognition, which also involved
images that suffered distortion type Gaussian noise in order to verify its robustness to the ability of discrimination
correlation Transformed Joint (JTC) classics.
Novel approaches for near and far field super-resolved imaging
Show abstract
In this paper we start by presenting one recent development in the field of near field imaging where a lensless
microscope is introduced. Its operation principle is based upon wavelength encoding of the spatial information through
non periodic holes array and right after decoding the spatial information using a spectrometer. In the second part of the
paper we demonstrate a remote super sensing technique allowing monitoring, from a distance, the glucose level in the
blood stream of a patient by tracking the trajectory of secondary speckle patterns reflected from the skin of the wrist.
Structure monitor system by using optical fiber sensor and watching camera in utility tunnel in urban area
Show abstract
This paper reports the measurement results of the utility tunnel (electric power and
communication) according to the adjacent expressway construction. And moreover, the
surveillance camera for the monitor is connected to the network, set up in joint premises in this
measurement, and it reports on the content observed overall.
Correction of deformed images in real time
Show abstract
Optical lens systems generally contain non-linear distortion artifacts that impose important limitations on the direct
interpretation of the images. Image processing can be used to correct for these artifacts, but due to the calculation-intensive
nature of the required distortion correction process, this is usually performed offline. This is not an option in
image-based applications that operate interactively, however, where the real-time display of distortion corrected images
can be vital. To this end, we propose a new technique to correct for arbitrary geometric lens distortion that uses the
parallel processing power of a commercial graphics processing unit (GPU). By offloading the distortion correction
process to the GPU, we can relieve the central processing unit (CPU) of doing this computationally very demanding task.
We successfully implemented the full distortion correction algorithm on the GPU, thereby achieving a display rate of
over 30 frames/sec for fully processed images of size 1024 × 768 pixels without the need for any additional digital image
processing hardware.
Nondestructive optical testing of the materials surface structure based on liquid crystals
Show abstract
Thin layers of nematic liquid crystals (NLCs) may be used as recording media for visualizing structural and microrelief
defects, distribution of low power physical fields and modifications of the surface. NLCs are more sensitive in
comparison with cholesteric and smectic LCs having super molecular structures. The detecting properties of NLCs are
based on local layers deformation, induced by surface fields and observed in polarizing microscope. The structural
surface defects or physical field's distribution are dramatically change the distribution of surface tension. Surface defects
recording becomes possible if NLC deformed structure is illuminated in transparent or reflective modes and observed in
optical polarizing microscope and appearing image is compared with background structure. In this case one observes not
the real defect but the local deformation in NLCs. The theory was developed to find out the real size of defects. The
resolution of NLC layer is more than 2000 lines/mm. The fields of NLC application are solid crystals symmetry,
minerals, metals, semiconductors, polymers and glasses structure inhomogeneities and optical coatings defects detecting.
The efficiency of NLC method in biophotonics is illustrated by objective detecting cancer tissues character and
visualizing the interaction traces of grippe viruses with antibodies. NLCs may detect solvent components structure in tea,
wine and perfume giving unique information of their structure. It presents diagnostic information alternative to dyes and
fluorescence methods. For the first time the structures of some juices and beverages are visualized to illustrate the unique
possibilities of NLCs.
Software configurable optical test system for refractive optics
Show abstract
SCOTS (software configurable optical test system) is a useful tool that can provide lens manufacturers with the ability to
evaluate the net performance of a lens system without the use of complex metrology systems and setups. This technique
is based on measuring the transverse ray aberrations of rays to obtain wavefront information using transmission
deflectometry, the refractive equivalent of reflection deflectometry.
Some work using deflectometry on refractive surfaces has been briefly reported in the past, where the power of a single
lens has been the measurement objective. Results showing the use of deflectometry on reflective optical surfaces, such
as the primary mirror of the Giant Magellan Telescope (GMT) show that this method has a large dynamic range in
which measurement accuracy is comparable with those of interferometric methods; generating interest on our part, to
investigate deflectometry for refractive systems in more detail.
In this paper, we focus on reporting initial tests using SCOTS by measuring simple refractive elements, such as 1"
diameter biconvex BK7 lenses. Results indicate a good agreement when comparing them with equivalent
MATLAB/ZEMAX wavefront measuring models, which include the measured lens parameters, where the estimated and
measured wavefront RMS values and spherical aberration Zernike coefficient agree on average to within 10nm. We also
investigate the effect of the chromatic aberration on the refractive optical system by collecting data using three different
wavelengths: 620nm, 550nm and 450nm. The alignment of the test setup was done rapidly and we used an LCD screen
with a pixel pitch of 0.1905mm. The camera used for the measurements was a simple digital CCD camera.
An alternative method for measuring the index profile of a gradient-index lens
Show abstract
An alternative method for measuring the index profile of the GRIN lens is proposed based on Fresnel's equations and the
common-path phase-shifting interfermetry. A light beam composing of the right- and the left- circularly polarized
components is obliquely incident on the tested GRIN lens and the reflected light passes through an analyzer. The light is
collected and imaged by an imaging lens to a CMOS camera. Four interferograms under different additional phases are
taken and Carre's phase-shifting method is used to calculate the full-field phase distribution. Next, the estimated data are
substituted into the special equations derived from the Fresnel's equations, and the index profile of the GRIN lens can be
obtained. Its validity has been demonstrated. It has both merits of the common-path interferemetry and the phase-shifting
interferemetry.
Measurements of extreme physical phenomena by Fourier fringe analysis, a review: from sub-Angstrom lattice distortion measurement to attosecond pulse phase measurement
Show abstract
In this talk we review and introduce some of the examples of successful applications of the Fourier transform method
(FTM) of fringe pattern analysis to the measurements of extreme physical phenomena, such as those involving ultra fast
optical pulses, extremely small atomic displacements, and unconventional electron wave or EUV light, and show how
the advantages of FTM are exploited in these cutting edge application areas.
Real-time numerical reconstruction of digitally recorded holograms
Show abstract
The numerical reconstruction of digitally recorded holograms has constituted the bottle neck for real-time digital
holography. The reconstruction process can be understood as the diffraction that undergoes a wavefront as it illuminates
the digitally recorded hologram. As this process is done numerically, the reconstruction of a M × N pixels hologram into
an image of similar dimensions is an operation with a Ο (M × N)2 complexity. The diffraction process can be represented
by a Fresnel transform or a scalable convolution of the recorded hologram. In these representations the numerical
reconstruction has a complexity of Ο (M × log N)2, still quite demanding computationally if the holograms are of 2048 × 2048 pixels. In this work, the power provided by a Graphics Processing Unit (GPU) is used to accelerate the numerical
reconstruction of digitally recorded holograms. The methodology is supported on the parallelization of typical Fresnel
transform and scalable reconstruction algorithms. On reconstructing holograms of 2048 × 2048 pixels, the reconstruction
is speeded up 20 times for the former method and 11 times for the scalable convolution. For holograms of 1024 × 1024,
the accelerated reconstruction methods allow for real-time digital holography.
Metal nanostructures for the enhancement of the Raman response of molecular adsorbates
Show abstract
Spectroscopic investigation of metallic nanostructures of different size and morphology is presented, with particular
focus on the capability of enhancing the Raman response of molecular adsorbates, namely on their SERS properties. In
this framework, we describe recent results obtained with Au/Ag nanocages and Au nanostars, which can be used
conveniently to shift the extinction spectra and the SERS activity up to the near infrared. In the case of nanostars, we
present a synthesis procedure which permits fine tuning of their morphology and extinction, thus allowing preparation of
structures with controlled SERS activity from 500 up to 1500 nm.
Analysis of cantilever beam test using digital holography
Show abstract
In the present work an interferometric approach based on the implementation of a digital holography setup is discussed.
It is used to determine interferograms of materials under small deformations. In order to do this, a fixed-free cantilever
beam subjected to a concentrated force applied at the free end is taken into account. The experimental procedure to
estimate displacements is carried out using digital Fourier transform holography (DFTH) technique. This is obtained
making a very simple modification in the classical setup architecture of the DFTH setup. It is also demonstrated the easy
and practical viability of the setup in an interferometric application for mechanical parameters determination.
Relative entropy of grayscale images degraded by bit-plane quantization and random noise
Show abstract
This paper presents an experimental study of the relative entropy of grayscale images degraded by bit-quantization
and additive random noise. Bit-plane quantization is produced by removing any number of selected bit-planes
from a given grayscale image, whereas noise is modeled additively using impulse, uniform, Gaussian, Poisson,
and Cauchy probability density functions. A comparison of the behavior of relative entropy with other image
measures such as the normalized mean square error, the signal-to-noise ratio, and the correlation coefficient is
also given for different levels of bit-plane quantization and parameter values of the aforementioned noise probability
density functions. An illustrative example is provided together with characteristic graphs that demonstrate
quantitatively the overall discrimination capability performed by the relative entropy measure.
Implementation of nonmonotonic logics by Fourier holography technique
Show abstract
An approach for fuzzy-valued nonmonotonic logics, based on the algebra of Fourier-dual operators, to be implemented
by Fourier-holography technique is proposed. Results of computer simulation based on experimentally implemented
logics are presented.
Butterflies' wings deformations using high speed digital holographic interferometry
Show abstract
A variety of efforts in different scientific disciplines have tried to mimic the insect's in-flight complex system.
The gained knowledge has been applied to improve the performance of different flying artifacts. In this
research report it is presented a displacement measurement on butterflies' wings using the optical noninvasive
Digital Holographic Interferometry technique with out of plane sensitivity, using a high power cw
laser and a high speed CMOS camera to record the unrepeatable displacement movements on these organic
tissues. A series of digital holographic interferograms were recorded and the experimental results for several
butterflies during flapping events. The relative unwrapped phase maps micro-displacements over the whole
wing surface are shown in a wire-mesh representation. The difference between flying modes is remarkably
depicted among them.
Interferometric characterization of joint optical tables
Show abstract
We present a straight forward and practical method for joining pneumatically floated optical tables with no
previous preparation. In order to demonstrate this method we joined two optical tables in an uncentered "T-shape"
using twenty four stainless steel plates (SSP), and used a Michelson interferometer to compare the stability
of the entire "T"-structure versus one of its parts alone, finding that they both show similar rigidity. We also
evaluated the performance of two different master-salve leg configurations by calculating the stress on the joint
and confirmed the calculations by Michelson interferometry. In terms of floor vibration damping, it was observed
that the performance of the system for the joined "T"-table seemed to be comparable to that of a single segment.
This method can significantly reduce costs of large optical tables and will be useful to extend existing optical
tables without manufacturer modification.
Invariant correlation by using vectorial signatures and spectral index
Show abstract
In this paper a non-linear correlation methodology to recognize objects is used. This new system is invariant to position,
rotation and scale. This digital system has a low computational cost to achieve a significant reduction of processed
information by using vectorial signatures. The invariant vectorial signatures are obtained from the information from both
the target image as well as problem image. In this way, each image has its rotational and scale vectorial signature
obtained through several mathematical transformations such as scale and Fourier transform. So, this method uses the
great capacities from the non-linear filters to discriminate between similar objects. Vectorial signatures are compared
using non-linear correlation. The result of this comparison is shown in a bi-dimensional plane where the x axis is the
result of the rotation correlation and the y axis is the result of the scale correlation. In addition, spectral index and
vectorial signature index are obtained through several mathematical transformations in order to recognize the objects in a
more simple way. 21 different fossil diatoms images were used. The results obtained are analyzed and discussed.
Digital system of invariant correlation to position and scale using adaptive ring masks and unidimensional signatures
Show abstract
Digital systems of invariant non-linear correlation to position and scale based on adaptive binary mask of concentric
rings and unidimensional signatures are useful tool in pattern recognition. With the modulus of the Fourier transform of
the image we obtain the invariance to translation. Using the Scale transformation and adaptive binary ring masks the
scale invariant is calculated. The discrimination between objects is done by non-linear correlation of the unidimensional
signatures assigned to the problem image and the target. In addition, working with unidimensional signatures reduce the
computational time considerably, achieving a step toward the ultimate goal, which is developing a simple digital system
that accomplishes recognition in real time at low cost.
Multi-user multiplexed scheme for decoding modulated-encoded sequential information
Show abstract
Encrypting procedures with multiplexed operations exhibit an inherent noise. We presented options to avoid background
noise arising from the non-decoded images. We have a coding mask corresponding to each single input object, thus
resulting in a static decrypting mechanism. Besides, if we manage the spatial destination of each decoded output, then we
avoid the noise superposition. In those schemes, the displaying output order was irrelevant. However, when we face a
sequence of events including multi-users, we need to develop another strategy. We present a multi-user encrypting
scheme with a single encoding mask that removes the background noise, also showing the decrypted data in a prescribed
sequence. The multiplexing scheme is based on the 4f double random phase encryption architecture and a theta
modulation method, which consists in superposing each encrypted information with a determined sinusoidal grating.
Afterwards we proceed to the completely encoded data multiplexing. In a multi-user scheme, we employ different
encrypting masks in the 4f optical setup for each user, and the same mask is employed for the user sequence. We store
the encrypted data in the single medium. After a Fourier transform operation and an appropriate filtering procedure, we
reach the sequence of isolated encrypted spots corresponding to the right user. With the aid of the pertaining decoding
mask, the user can decrypt the sequence. We avoid the noise by the appropriate choice of the modulating gratings pitch
as to elude the overlapping of spots at the Fourier plane, which is the cause of information degradation.
Performance of composite correlation filters for object recognition
Show abstract
Correlation filters have become an important tool for detection, localization, recognition and object tracking in digital
media. This interest in correlation filters has increased thanks to the processing speed advances of the computers that
enable the implementation of digital correlation filters in real-time. This paper compares the performance of three
correlation filters in the activity of object recognition, specifically human faces with variations in facial expression, pose,
rotation, partial occlusion, illumination and additive white Gaussian noise. The analyzed filters are k-law, MACE and
OTSDF. Simulation results show that the k-law nonlinear composite filter has the best performance in terms of accuracy
and false acceptance rate. Finally, we conclude that a preprocessing algorithm improves significantly the performance of
correlation filters for recognizing objects when they have variations in illumination and noise.
Analysis of cracks and damages in optical elements by a swept-source optical coherence tomography technique
Show abstract
Optical coherence tomography (OCT) is a non- invasive technique where a near-infrared laser beam penetrates a sample
and through the analysis of its scattered light information about the internal structure of the sample is calculated.
Although OCT is mainly used in medicine its application to areas of enginery has been increased recently. Important
features of recent OCT systems allow us to determine accurately volumetric structure not only slices. In this works we
report such volumetric analysis applied to the study of scratches and damages in optical elements in order to quantify not
only the scratch sizes but also its depths. This study is compared with an Schlieren technique. Experimental results are
presented. The finding reveals clearly the faults locations which may be an attractive results for the optical work shop
and the application of norms.
Optical and mechanical nondestructive tests for measuring tomato fruit firmness
Ricardo A. Manivel-Chávez,
M. G. Garnica-Romo,
Gabriel Arroyo-Correa,
et al.
Show abstract
Ripening is one of the most important processes to occur in fruits which involve changes in color, flavor, and texture. An
important goal in quality control of fruits is to substitute traditional sensory testing methods with reliable nondestructive
tests (NDT). In this work we study the firmness of tomato fruits by using optical and mechanical NDT. Optical and
mechanical parameters, measured along the tomato shelf life, are shown.
Near IR diodes as illumination sources to remotely detect under-drawings on century-old paintings
Show abstract
Mexico possesses a large cultural heritage of paintings, elaborated after the European explorers encountered the New World.
The interest in documenting these treasures was recently renewed, with the development of nondestructive remote
techniques. We examined an undocumented painting for the presence of any invisible signatures, dates, or under-drawings.
We employed several illumination-detection schemes, including IR broadband and LED arrays to achieve this purpose. We
made visible the signature at about 1 μm and the date at 1.2 μm.
A dynamical light scattering technique and its application in viscoelastic networks in soft matter
Erick Sarmiento-Gomez,
Julian Masasue Galvan-Miyoshi,
Rolando Castillo
Show abstract
In this paper, we present a dynamic light scattering technique using diffusing wave spectroscopy to track the
dynamics of colloidal particles embedded in a complex fluid which allows us to obtain structural and dynamical
information of a transparent viscoelastic material. Scattered light of a single speckle is detected by a photomultiplier
tube and the time correlation function of light intensity is calculated using a temporal average. If the
particles can not explore the entire phase space, temporal average and ensemble average are not the same. This
is a necessary condition to relate ensemble average from the scattering by many particles to intensity temporal
fluctuations. To overcome non-ergodicity for large lag times, a CCD camera is used for the acquisition of the
scattered light were pixels form an array of detectors which enables us to perform thousands of simultaneous
experiments. In this manner, the time correlation function is obtained directly by taking the ensamble average
instead of using a temporal average. For short lag times, the non-ergodicity problem can be avoided by remixing
the scattered light coming from the sample by the use of a slowly rotating diffuser disk placed before the collection
optics of the photomultiplier tube. This procedure provides a true ensemble-averaged time correlation function
over ~ 7-8 decades of time. As an example of the application of this technique, the dynamics of microspheres
embedded in cross-linked polymer matrix, namely, an acrylamide-bisacrylamide gel is studied. This polymer network
is known to swell or shrink by changing the solvent composition. The description of the arrested dynamics
of the microspheres can be obtained, as well as the viscoelastic properties of the polymer network at different
cage sizes.
Encoding degree testing in a 4f architecture
Show abstract
The distribution of the encrypted information at the output of an encoding system is of major concern. When the
encrypted information is conveyed to the final user, the finite size of the recording medium affects the quality of the
encoded information. In this case, we face possible information degradation when recovering. In the present contribution
we focus our attention on the finite size of the recorder medium in an actual experimental situation. In order to improve
the quality of the decrypted data, we study the role that both the scattering element size of the masks and the input object
size play in the encrypting system. Therefore, we analyze the optimal spatial distribution of the encoded information at
the output of a 4f encrypting system. We present examples that support our proposal.
Real-time parallel method for quadrature transform estimation and 3D surface measurement
Show abstract
A massively parallel real-time algorithm for the estimation the dynamic phase map of a vibrating object is
presented. The algorithm implements a Fourier-based quadrature transform and temporal phase unwrapping
technique, and was implemented using CUDA, a general purpose computing and development environment for
NVIDA GPU's. The algorithm was tested on a 64 × 640 fringe patterns sequence achieving a processing rate
higher than 2270 frames per second (fps).
Solar concentrator with diffuser segments
Show abstract
Solar energy systems use concentrating optics with photovoltaic cells for optimizing the performance. Advanced
concentrators are designed to maximize both the light collection and the spatial uniformity of radiation. This is important
because irradiance uniformity is critical for all types of photovoltaic cells. This is difficult to achieve with traditional
concentrators, which are built with polished optical surfaces. In this work we propose a new concept of solar
concentrator which uses small diffuser segments in key points to increase the irradiation uniformity. We experimentally
demonstrate this new concept by analyzing the effects on both efficiency and irradiance uniformity due to the
incorporation of scattering ribbons in a compound parabolic concentrator.
Subsampling technique to enhance the decoded output of JTC encrypting system
Show abstract
Optical systems have physical restrictions that impose limits in the finest spatial feature that can be processed. In this
work we combine a subsampling procedure with a multiplexing technique to overtake the limit on the information that is
processed in a JTC encryption system. In the process the object is divided in subsamples and each subsample is
encrypted separately. Then the encrypted subsamples are multiplexed. The encryption of the subsamples is performed in
a real optical JTC encrypting system. The multiplexing and the decryption process are carried out by means of a virtual
optical system. Experimental results are presented to show the validity of the proposal.
Unsupervised color image segmentation using a lattice algebra clustering technique
Show abstract
In this paper we introduce a lattice algebra clustering technique for segmenting digital images in the Red-Green-
Blue (RGB) color space. The proposed technique is a two step procedure. Given an input color image, the
first step determines the finite set of its extreme pixel vectors within the color cube by means of the scaled
min-W and max-M lattice auto-associative memory matrices, including the minimum and maximum vector
bounds. In the second step, maximal rectangular boxes enclosing each extreme color pixel are found using
the Chebychev distance between color pixels; afterwards, clustering is performed by assigning each image pixel
to its corresponding maximal box. The two steps in our proposed method are completely unsupervised or
autonomous. Illustrative examples are provided to demonstrate the color segmentation results including a brief
numerical comparison with two other non-maximal variations of the same clustering technique.
Organic solar cells under the BHJ approach using conventional/inverted architectures
Show abstract
The search of clean and renewable energy sources is one of the most important challenges that mankind confronts.
Recently there has been a notable interest to develop organic photovoltaic (OPV) technology as a mean of renewable
energy source since it combines low-cost and easy fabrication. Most of the efforts have been directed to increase the
efficiency, leaving aside the durability of the organic materials, however, a new architecture known as inverted solar cell
might bring a never seen durability (years) that could make possible large scale applications of this technology. Here are
presented the results we achieved using both, the conventional and inverted architectures employing as organic donor
(D) the very well known semi-conducting polymer P3HT, in mixtures with the acceptor (A) fullerene PC61BM. The
morphology of thin polymer films prepared by using the spin coating technique was analyzed by AFM. For the
conventional architecture the cells were fabricated following the structure ITO/PEDOT:PSS/P3HT:PC61BM/Wood´s
metal, where the Wood´s metal cathode is an alloy that melts at 75 °C. For the inverted architecture the structure
ITO/ZnO/P3HT:PC61BM /PEDOT:PSS/(Ag, Cu or Silver paint) was used, where ITO worked as cathode by switching
its work function through the introduction of ZnO nanoparticles. Under tests using Xenon lamp irradiation at 100
mW/cm2, the conventional and the inverted architectures produced efficiencies of 1.75 % and 0.5 %, respectively. For
both architectures the chosen back-contact materials (Wood´s metal and silver paint) allowed us to easily make the OPVs
cells without the need of vacuum steps.
The influence of the temperature in the UV-Vis spectrophotometers calibration
J. Medina Márquez,
J. Carranza Gallardo
Show abstract
The study of the influence of temperature as a variable during the spectrophotometer calibration is very important to
many laboratories, due to the fixed temperature imposed by the national laboratory (CENAM). This gives us an
invaluable insight to know in ahead that we do not have to be tied up to a unique temperature inherited by CENAM. In
this manner we can increase our scope in which we can accomplish a trustful metrological calibration in a wide
temperature range. For this reason, in this work a study of the temperature influence in the calibration of swept UV-Vis
spectrophotometers is shown. The temperature interval was set between 18°C to 31 °C, and glass filters of neutral
density at 1%, 50%, and 90% were used as a reference approved materials to calibrate the photometric scale and a
holmium oxide glass filter was used to calibrate the wavelength scale. An ANOVA analysis was used (variance analysis)
and the obtained results have a confidence of 95,45%. The results of this study show that the temperature is not an
influence variable during the spectrophotometer calibration in the interval of 18°C to 31°C, which allows us to simplify
the uncertainty estimation model.
Optical granulometry by digital image processing
Show abstract
For several decades the field of engineering geology, has had several difficulties to characterize properties of
sedimentary particles. These particles are characterized by a multitude of sizes and shapes. For measuring the sizes
there are a number of instruments based on different principles. However, the use of these instruments is not very
widespread. The size of sediment particles covers several orders of magnitude therefore, the instruments have been
developed do not meet all requirements. Several authors have demonstrated the feasibility to perform these tests by
means of digital image processing. In this paper we propose to obtain optical particle size, morphological analysis and
density, in a range of 30 microns to 50 mm. To this end we propose two assemblies that cover the range of sizes. In the
proposed assembly is used as transport fluid particles. The fluid and allow a mechanism to disperse the sample, this
solves the problem of segmentation in digital image processing. It uses a back-illuminated light for accurate
measurement of particles due to the complexity of its component phases. By digital image processing can be 41
measurements on each particle. Furthermore allows morphological analysis using the Fourier method. A tracking
algorithm to determine the density of the particles according to Stokes' law. Experiments demonstrate the accuracy and
repeatability of this method compared with other methods of measurement.
Unified theory of phase unwrapping approaches in multiwavelength interferometry
Show abstract
Multi-wavelength interferometry (MWI) has a long tradition and provides a solution to a number of applications in the
field of optical metrology. In MWI phase unwrapping procedures are usually based on beat wavelength approaches,
Chinese Remainder Theorem (CRT) techniques, or the method of Excess Fractions (EF). Each of these unwrapping
approaches has distinct advantages making it suitable for a given application. Beat wavelength and CRT based
approaches offer a direct calculation of integer fringe order, however, the unambiguous measurement range (UMR) is
limited by the available measurement wavelengths. On the other hand, EF offers many alternative sets of wavelengths to
achieve a large UMR with high reliability; however, the calculation of the integer fringe order involves a large number of
computational steps. In this work, a unified theory of beat wavelength, EF and CRT approaches is reported. It is shown
that the calculation of the integer fringe order requires a low computational effort, which hitherto had only been possible
for CRT and beat wavelength approaches, whilst offering flexibility in choosing the measurement wavelengths for a
given UMR, which had only been the case for EF. As the model can be used in a predictive way to determine the UMR
and measurement reliability it is possible to define optimization criteria that are based on parameters which are
dependent on the choice of the measurement wavelengths.
Invariant correlation to position, rotation, and scale using one-dimensional composite filters
Show abstract
A nonlinear correlation digital algorithm invariant to position, rotation and scale using a binary mask is presented. In
order to analyze this new identification digital system binary and gray images are used. The problem images had a
±30% of maximum scale variation with respect to the target. Some composite filters had a very good performance in
this range. The rotation goes from 0° to 359°. Concentric binary rings masks were elaborated, from the Fourier
transform, using the real or the imaginary part. The signatures of the problem image and the target were obtained from
the ring mask. The objective is identifying a specific target no matter the position, rotation or scale presented in the
problem image. A statistical analysis was done to know the mean correlation confidence level. In this work, a new, fast
and functional position, scale and rotation invariance pattern recognition digital system was obtained.
Assigning pseudocolor to 3D data arrays
Show abstract
This document presents an Optical Model to visualize 3-D data arrays, taken from Computer Tomography (CT). The Optical Model simulates a planar wave front of light that goes through the materials of different refractive index. With this method we assign pseudo-color to any of the materials (skin, bone, or soft tissue) that are in the volume.
Tomato classification based on laser metrology and computer algorithms
Otoniel Igno Rosario,
J. Apolinar Muñoz Rodríguez,
Haydeé P. Martínez Hernández
Show abstract
An automatic technique for tomato classification is presented based on size and color. The size is determined
based on surface contouring by laser line scanning. Here, a Bezier network computes the tomato height based
on the line position. The tomato color is determined by CIELCH color space and the components red and
green. Thus, the tomato size is classified in large, medium and small. Also, the tomato is classified into six
colors associated with its maturity. The performance and accuracy of the classification system is evaluated
based on methods reported in the recent years. The technique is tested and experimental results are presented.
Hybrid super-resolving pupils with smooth profile
Noé Alcalá Ochoa,
J. E. A. Landgrave,
Y. Hermosillo,
et al.
Show abstract
One form of achieving super-resolution consists in reducing the size of the Point Spread Function (PSF)
of a diffraction-limited optical system. For this end, good results have been obtained by means of pupils with
discontinuous profiles. When devices such as deformable mirrors are used to generate such pupils,
however, these cannot be accurately reproduced. To overcome this limitation, we developed a method based
on a Bessel series expansion to design pupils with smooth profiles, and found that, properly designed, pupils
with continuous profiles will perform equally well, and in some respects better, than pupils with
discontinuous ones.
Vibration measurement in non-rigid test environment with speckle interferometry
Show abstract
We propose a new method for vibration measurement in non-rigid test environment with electronic speckle pattern
interferometry (ESPI). The ESPI is useful for non-contact, real-time analysis of vibration. This method needs rigid test
environment, however. When the interferometer and a vibration surface are on a non-rigid table or their environments
are separated, especially at manufacturing areas, high-amplitude, low-frequency noise fluctuation overwhelms a
vibration signal and the amplitude fringes disappear. We use electronic shutter function of a TV camera and reduce
exposure time of an image sensor. With the time reduction, we may extract an image from many input images, during
whose acquisition time noise fluctuation turns back and its magnitude is so small that the vibration signal goes to be
included in the image. We accumulate the images and increase the contrast of the amplitude fringe map.
We evaluated usefulness of this method with circular saw vibration. The interferometer and the saw are fixed on a rigid
board and the noise fluctuation is electronically superposed on the vibration signal with sine wave. This method is
successful for a fluctuation amplitude of 60μm.
Geometrical properties of microstructures by Mirau interferometric objective microscope
Show abstract
This paper describes a micro-topography measurement system using a Mirau interferometric microscope objective. Such
system is a non-invasive, full-field, economical, and compact. The interferometer device consists of a beam splitter that
permits send a portion of the light to the sample surface and other part to a reference surface. Reflected light from these
surfaces are combined to form interference fringes which are captured by a CCD camera. For each local point on the
surface target, there is a distance from the Mirau microscope objective lens. Then, each fringe provides the locus of
points of equal phase in the interferogram image. Contour lines corresponding to the surface target topography are
extracted from the interferograms using digital image processing. Phase-stepping technique have been used in order to
have a phase map which is unwrapped and mapped to a full-field microscopic data topography of the surface target.
Object target is mounted on computer controlled stage with capability of linear movements of the order of nanometers.
With this, the phase-stepping technique was done. For calibrating, a step-in-shape made of thin film on a glass substrate
is built up. The obtained depth resolution is of 15 ± 4 nm, employing the interferometric system. Experimental results
were compared with an Atomic Force Microscope, (AFM) giving an overall error of 17 nm on a 33μm × 45μm field of
view. An application for integrated optics on-chip quality control is suggested.
Parallel approach to MEMS and micro-optics interferometric testing
Show abstract
The paper presents the novel approach to an interferometric, quantitative, massive parallel inspection of
MicroElectroMechanicalSystems (MEMS), MicroOptoElectroMechanical Systems (MOEMS) and
microoptics arrays. The basic idea is to adapt a micro-optical probing wafer to the M(O)EMS wafer under
test. The probing wafer is exchangeable and contains one of the micro-optical interferometer arrays based on:
(1) a low coherent interferometer array based on a Mirau configuration or (2) a laser interferometer array
based on a Twyman-Green configuration. The optical, mechanical, and electro-optical design of the system
and data analysis concept based on this approach is presented. The interferometer arrays are developed and
integrated at a standard test station for micro-fabrication together with the illumination and imaging modules
and special mechanics which includes scanning and electrostatic excitation systems. The smart-pixel approach
is applied for massive parallel electro-optical detection and data reduction. The first results of functional tests
of the system are presented. The concept is discussed in reference to the future M(O)EMS and microoptics
manufacturers needs and requirements.
Optical analysis of electro-optical systems by MTF calculus
Show abstract
One of the widely used methods for performance analysis of an optical system is the determination of the
Modulation Transfer Function (MTF). The MTF represents a quantitative and direct measure of image
quality, and, besides being an objective test, it can be used on concatenated optical system. This paper
presents the application of software called SMTF (software modulation transfer function), built in C++ and
Open CV platforms for MTF calculation on electro-optical system. Through this technique, it is possible to
develop specific method to measure the real time performance of a digital fundus camera, an infrared sensor
and an ophthalmological surgery microscope. Each optical instrument mentioned has a particular device to
measure the MTF response, which is being developed. Then the MTF information assists the analysis of the
optical system alignment, and also defines its resolution limit by the MTF graphic. The result obtained from
the implemented software is compared with the theoretical MTF curve from the analyzed systems.
Metrological analysis of the human foot: 3D multisensor exploration
Show abstract
In the podiatry field, many of the foot dysfunctions are mainly generated due to: Congenital malformations, accidents or
misuse of footwear. For the treatment or prevention of foot disorders, the podiatrist diagnoses prosthesis or specific
adapted footwear, according to the real dimension of foot. Therefore, it is necessary to acquire 3D information of foot
with 360 degrees of observation. As alternative solution, it was developed and implemented an optical system of threedimensional
reconstruction based in the principle of laser triangulation. The system is constituted by an illumination unit
that project a laser plane into the foot surface, an acquisition unit with 4 CCD cameras placed around of axial foot axis,
an axial moving unit that displaces the illumination and acquisition units in the axial axis direction and a processing and
exploration unit. The exploration software allows the extraction of distances on three-dimensional image, taking into
account the topography of foot. The optical system was tested and their metrological performances were evaluated in
experimental conditions. The optical system was developed to acquire 3D information in order to design and make more
appropriate footwear.
Spatio-temporal experiments of volume elastic objects with high speed digital holographic interferometry
Show abstract
The optical non-destructive digital holographic interferometry (DHI) technique has proven to be a powerful tool in
measuring vibration phenomena with a spatial resolution ranging from a few hundreds of nanometers to tens of
micrometers. With the aid of high speed digital cameras it is possible to achieve simultaneously spatial and temporal
resolution, and thus capable of measuring the entire object mechanical oscillation trajectory from one to several cycles. It
is important to mention that due to faster computers with large data storage capacity there is an increasing interest in
applying numerical simulation methods to mimic different real life objects for example, in the field of modern elastic
materials and biological systems. The complex algorithms involved cannot render significant results mainly due to the
rather large number of variables. In order to test these numerical simulations some experiments using optical techniques
have been designed and reported. This is very important for example in measurements of the dynamic elastic properties
of materials. In this work we present some preliminary results from experiments that use DHI to measure vibrations of an
elastic spherical object subject to a mechanical excitation that induces resonant vibration modes in its volume. We report
on the spatial and temporal effects that by their nature have a non-linear mechanical response. The use of a high speed
CMOS camera in DHI assures the measurement of this nonlinear behavior as a sum of linear effects that happen during
very short time lapses and with very small displacement amplitudes. We conclude by stating that complex numerical
models may be compared to results using DHI, thus proposing an alternative method to prove and verify the
mathematical models vs. real measurements on volumetric elastic objects.
Digital holography system for topography measurement
Show abstract
The optical characteristics of Diffractive Optical Elements are determined by the properties of the photosensitive
film on which they are produced. When working with photoresist plates, the most important property is the
change in the plate's topography for different exposures. In this case, the required characterization involves a
topographic measurement that can be made using digital holography. This work presents a digital holography
system in which a hologram's phase map is obtained from a single recorded image. The phase map is calculated
by applying a phase-shifting algorithm to a set of images that are created using a digital phase-shifting/tilteliminating
procedure. Also, the curvatures, introduced by the imaging elements used in the experimental setup,
are digitally compensated for using a polynomial fitting-method. The object's topography is then obtained from
this modified phase map. To demonstrate the proposed procedure, the topography of patches exposed on a
Shipley 1818 photoresist plate by microlithography equipment-which is currently under construction-is shown.
Michelson microscope interference objective for micro-structure topography measuring
Show abstract
Nowadays, the trends of miniaturization of sensors and inspection devices have been of major importance in science and
technology. The characterization of microchips, integrated circuits, MEMS, and micro-sensors is important to determine
their proper operation. Due to their element small size may have structural fails for improper handling of them. This
paper proposes the use of a Michelson interferometric objective for the determination of topographical features in
materials at micro and nanoscale level. The main advantage of this method is its non-invasive nature that allows testing
in soft materials without damage. The Michelson interferometric microscope objective with a magnification of 5X
illuminated with a 632nm He-Ne laser is used. Fringes that allow the study of the topography of these structures are
properly analyzed. The acquisition of the interferograms was performed by a CCD, which are handled by the method of
phase-stepping. An integrated circuit of a CCD as target is used. A reconstruction of the microscopic topography of the
sample produced results with a statistical error in the topography of 12nm. Application of this method is to conduct
quality control tests in manufacture of electronic components such as micro-chips and integrated circuits.
Quantitative analysis on key estimation by known-plaintext attacks to DRPE
Show abstract
Double Random Phase Encoding (DRPE), which is a typical optical encryption technique, has been reported to be
vulnerable to Known Plaintext-Attacks (KPAs) using a Phase Retrieval Algorithm (PRA). But the reported case in which
the encryption key is successfully estimated was that the plain image was rather simple such as the image of a character.
In addition, although Phase Only DRPE (PO-DRPE) was proposed to achieve more resistance to the KPA than Complex
DRPE (C-DRPE) in which both amplitude and phase components are used as an encrypted image, no quantitative results
about the relationship between the vulnerability and the plaintext image. In this paper, we show the result of quantitative
analysis on KPA by PRA to C-DRPE and PO-DRPE, for the plaintext images of different characteristics. As a result of
experiment, KPA to C-DRPE succeeded to estimate the correct key while the probability of success became lower when
the number of non-zero pixel increases in the plaintext image. However, KPA to PO-DRPE enabled to estimate only
"singular" keys, which are effective for no more than given plaintext/ciphertext image pair and far different from the
correct encryption key. We also conducted KPA using two plaintext-ciphertext image pairs for KPA. In the case when
two plaintext-ciphertext image pairs were given to KPA, the cryptanalysis succeeded with higher probability than the
case of one. Moreover, the probability of success in the KPA was high even in PO-DRPE.
Minimum image resolution for shape recognition using the generic Jacobi Fourier moments
Show abstract
We consider the use of Jacobi-Fourier moments for the classification of objects from motion blurred images. A set of
numerical features are extracted from an image. These features are invariant to the changes in the scale, orientation,
position, and illumination of the objects in the vision field. The test images used here have been acquired when the
objects are vibrating at different frequencies and moving at constant velocity. The blur extent by image motion can be
obtained using moment descriptors of the motion. Also, the acquisition system is characterized by means the optical
transfer function (OTF); which can be computed by the geometric moments of motion function of the object centroid.
The classification method is tested using images from objects which have intrinsically little differences between them.
Experimental results show that, the proposed classification method based in Jacobi Fourier moments can be well
addressed to grade images smeared by motion. A comparison of effectiveness is done with motion descriptors based on
geometric moments.
Comparative analysis of directional filtering techniques in fringe patterns
N. Escalante,
J. Villa,
I. De la Rosa,
et al.
Show abstract
We present a comparison of some methodologies that exist for directional filtering of fringe patterns. An important task in fringe image processing is the noise filtering. The implementation of linear filters is not always a proper procedure in the presence of high density fringes because the signal and noise are mixed in Fourier space. The objective of this report is to carry out a comparison of existing procedures to determine which of them provides a better image estimation. The techniques considered in this work are: Regularized Filters (RQCF), Oriented spatial filter masks (OSFM), Second-Order Oriented partial differential equations (SOPDE) and Directional filters (DF). To compare these techniques, we analyze their performance for different noise levels, using synthetic fringe images.
3D displacement and strain measurements using simultaneously three lasers
Show abstract
In this work we present an extension of the use of three different lasers and only one high resolution monochrome sensor.
Besides the advantage to obtain the 3D deformation in just two images it is now possible due the geometry of the optical
setup to obtain the strain gradients in the object. The system records two consecutive images where each one contains
three holograms in it. This configuration gives the opportunity to use long coherence length lasers which allows the
measurement of large object areas. A series of digital holographic interferograms are recorded for a particular metallic
sample during a well known mechanical deformation. From the system it is possible to obtain in just a couple of images
the orthogonal displacement components u, v and w and then the strain gradient maps. Latter gives more information
about the mechanical response for an object during a micro deformation.
Retrieval of spectroscopic information from the Tonantzintla Schmidt camera archival plates
Show abstract
There is a relevant and growing effort in Astronomy to store observations in Virtual Observatories to make better use and
exploitation of modern and archival data. In that perspective, we are in the process of not only digitalizing the
Tonantzintla Schmidt Telescope plate archival (about 15000 plates from 1942-1995), but actually developing a semi-automatic
system to process the large amount of direct-imaging and objective-prism data into a homogenous and
calibrated set, in order to create an astronomically useful catalogue for data mining and analysis. In particular, for the
4120 spectroscopic plates, the system consists of a series of algorithms that: locate and extract spectra; determine and
apply the proper wavelength calibration; carry on the astrometry solution; correlate the astrometry with direct images of
the archive (when available); and to label all identifiable objects. In this work we discuss the overall strategy to be
implemented and present preliminary results.
Comparison of background-oriented Schlieren and fringe deflection in temperature measurement
Show abstract
We report the results of a comparison analysis of the accuracy of two optical techniques which are based on ray
deflection, background-oriented schlieren (BOS) and fringe deflection (FD). In both techniques, a camera registers
images of a spatial pattern displayed on a screen: for BOS, spots randomly located; for FD, straight fringes. Two
images corresponding to two different states of a phase object are then compared: with and without the object. After
introducing the object, the corresponding spatial structures undergo displacements that are proportional to the change
of index of refraction. The displacements are calculated by digital correlation in BOS, and by phase retrieval in FD.
Therefore, by both techniques, displacement maps of numerically-simulated phase objects are obtained. Preliminary
results show for FD, higher accuracy and less numerical processing.
Phase unwrapping using morphologic processing
Show abstract
A simple method for phase unwrapping is proposed. When phase is smooth, continuous and slightly noisy,
morphological processing can be used to estimate the unwrapped phase. The application of morphological processing
converts the continuous (real) range [-π, π) into a discrete (integer) range. This domain transformation
may allow an increase of speed performance in the unwrapping phase processing. Since the wrapped phase is
modulo 2π, it is possible to delimit regions with 4-connectivity that allows the proper phase map estimation.
The maximum intensity of the noise that allows a good reconstruction of the original phase map was 2.
Micrometric measurement of thermally induced efforts using digital holographic interferometry
Freddy Monroy,
J. Garcia-Sucerquia
Show abstract
The change of temperature of an object introduces variation of the objects dimensions. These
dimensional changes that are in the micrometer scale, can have undesired consequences as for
example the decoupling of soldering points in electronic circuits. In this work we present a system
based on digital interferometry to quantify the dimensional change induced on an electronic circuit
board as it operates. In digital holographic interferometry of double exposure two holograms of the
object are registered for different temperatures. The holograms are registered by a solid state
detector and transferred to a computer; thereafter the recordings are reconstructed numerically using
Fresnel's approximation. The amplitude and the phase of the complex optical field reflected by the
object can be recovered. The resulting phase map is converted into micrometer dimensional
variations by means of a lookup table generated previously. The lookup table is computed by
calibrating phase maps obtained when known mechanical displacements are introduced over an
object. We present experimental results of deformations in the range of 0, 5 μm to 4 μm for a regular
circuit board.
Discrete Wigner distribution function applied on images of quasi-point source objects in coherent illumination
Show abstract
In this work, experimental results are obtained from the behavior of the Discrete Wigner Distribution Function (DWDF),
when is applied on a detected image of an object of small dimensions, non-resolved by the optical system (OS). The
object is illuminated with a laser source. We verify that for the average of several detected images the DWDF is positive
inside a frequency interval of four times the bandwidth of the OS. However, when the object is not a quasi-point source
the DWDF has positive and negative values inside the same interval. This is an indication that in this case the object is
resolved by the OS. Numerical and experimental results are shown and compared to support this conjecture.
Optical-digital restoration of out-of-focus color images detected in microscopy
Show abstract
An optical-digital method is proposed for restoring trichromatic images out-of-focus, detected with a monochromatic
CCD. The optical system (OS) is a microscope working in bright field mode and the source of illumination is
polychromatic. To carry out the restoration, an estimated of the intensity point spread function is obtained from the
image of a non-resolved object (quasi-point source) by the OS in three wavelengths. From the image of the quasi-point
source, its spectrum is calculated for obtaining the optical transfer function associated with each wavelength. The
Wiener filter is built with the spectrum, and the restoration is made for each color. By an addition of the three restored
images, an estimated of the trichromatic object is recovered. The obtained results and conclusions are presented.
Experimental results of phase retrieval with reduced noise using inline digital holography and an iterative method
Show abstract
Digital holographic microscopy is a method used to retrieve microscopic phase objects. However, the limited CCD
bandwidth, used to record the hologram, and the aberrations of imaging lens add some noise into the retrieval process. In
this context, the use of referenceless on axis digital holography is highly convenient due to the simplification of the
required optical setup. However, the amount of noise, due to the conjugate and zero-order terms in the holograms tend to
increase, because these hologram terms are overlapped with the signal term. We propose to enclose the object in a pupil
and use this information to obtain an approximation of the object phase. This approximation is used in an iterative
method, where the recovered field is cleaned from the conjugate and zero order hologram terms. Moreover, we show that
the distortion introduced by loss of high frequency information, in the retrieval process, can be compensated with the
iterative method. The simulation of this method had been proved with good results and they present a fast convergence
of the algorithm. In this work we present the first experimental results applying this method.
Wendland radial basis functions applied as filters on computed tomography
Show abstract
Wendland radial basis functions are applied as an alternative solution to the interpolation problem when the filtered back
projection algorithm is used in computed tomography. Since we have a regular grid of data points and these functions are
compactly supported, the interpolation can be made as a fast filtering process rather than solving a typical linear system
of equations. This allows us to apply the Error Kernel method, which gives details of the approximation quality in the
frequency domain, when we make interpolation with basis functions such as the B-splines. The Error Kernel provides us
a direct comparison between Wendland functions and B-splines. The comparison shows that the Wendland functions can
offer the same interpolation quality of the B-splines when the support is large, but with a small support the performance
is poor. We see this behavior making tomographic reconstructions with different Wendland functions and also with
different supports. A numerical experiment consisting of successive image rotations to an image was performed to verify
the similarities between the Wendland functions and B-splines.
Analysis of near field microwave and conventional optical images
Show abstract
In this work we present near field microwave images of microelectronic circuits and their interpretation to
complement the conventional optical analysis. We show a highly simplified design of a resonant probe with
dynamically tunable capacitive coupling and with high sensitivity. Images were obtained by measuring the
microwave reflection coefficient operating a 7 GHz. This design represents a simplified and highly effective
approach to implementing near field microwave microscopy.
Image segmentation using a hybrid technique by combining optical and digital methods
Show abstract
We present an image segmentation method based on the use of an optical technique for detection of contours (as a
preprocessing stage) and a posterior digital segmentation algorithms. The contouring technique is utilized to find an
accurate contour and it is based on the polarization features of the twisted-nematic liquid-crystal displays (TNLCDs).
TN-LCDs are manufactured to work between a crossed polarizer-analyzer pair. When the analyzer is at 45 deg (instead
of 90 deg) with respect to the polarizer, one obtains an optically processed image with pronounced outlines (dark
contours) at middle intensity. On other hand, the segmentation algorithms are based on active shape models or snakes.
Experimental results show that the proposed technique yields accurate segmentation for low-contrast images. Also, we
demonstrate that this hybrid-system has a better performance than purely digital algorithms.
Study of thermal properties of metallic samples AZ91E/ALN
Show abstract
Using the open photoacoustic cell technique, we obtained the spectra of the photoacoustic signal amplitude as a function
of the modulation frequency of the incident radiation. From these spectra we determined the thermal diffusivity in Mg-
AZ91E/AlN metal matrix composite with a magnesium alloy of around 9% aluminum and 1% zinc, the aluminum
nitrade (AlN) is a ceramic with relationship AlN/AZ91E with ratio 1:1. The photoacoustic signal amplitude in the region
thermally thick and optically opaque is used to calculate the thermal diffusivity of the Mg-AZ91E/AlN material and the
results obtained are shown.
Measurements of the tympanic membrane with digital holographic interferometry
Show abstract
In this paper a digital holographic interferometry (DHI) system with three object-illumination beams is used for
the first time to detect and measure micrometer deformations on the surface of a tympanic membrane. Using this
optical setup allows all three object displacement components x, y, and z, to be independently calculated. The
corresponding deformations are registered using a cw laser in stroboscopic mode and a CCD camera
synchronized to the excitation acoustic wave that produces a resonant vibration mode on the tympanic
membrane surface. A series of digital holographic interferograms record the displacements undergone by the
tympanic membrane and from them full field deformation phase maps are obtained. From the latter it is possible
to observe the displacement of the tympanic membrane in response to the sound pressure. The study was
performed on the tympanic membrane taken from a post-mortem cat. The results show the feasibility to apply a
similar optomechanical arrangement for the study in humans, representing an alternative technique for the study
of pathologies in the tympanic membrane.
Characterization of acoustically induced deformations of human tympanic membranes by digital holography and shearography
Show abstract
Recently, we introduced a Digital Optoelectronic Holographic System (DOEHS) for measurement of acoustically
induced deformations of the human tympanic membrane (TM) in order to study and diagnose pathologic conditions of
the middle-ear. The DOEHS consists of laser-delivery illumination (IS), optical head (OH), image-processing computer
(IP), and positioning arm (PS) subsystems. Holographic information is recorded by a CCD and numerically
reconstructed by Fresnel approximation. Our holographic otoscope system is currently deployed in a clinic and is
packaged in a custom design. Since digital holography is a high sensitivity measurement technique and the interfering
light waves travel along different paths, it makes measurements acquired by DOEHS susceptible to external vibrations.
In order to avoid this susceptibility, we are testing a shearography setup as OH. Shearography presents same advantages
as holographic interferometry, but it is less susceptible to vibration and external noise, which is a characteristic needed
for the use of our techniques in a clinical environment. In this paper we present work in progress in our development of a
shearography technique based on a Mach-Zehnder configuration as OH and demonstrate its application by quantifying
vibrations modes in thin membranes, including human TM. Results are compared with those obtained with DOEHS.
Speckle displacement in holographic and speckle metrology
Show abstract
Speckle patterns appearing in laser-illumination of a rough surface show dynamic changes when the surface is deformed
or illumination is moved. This change is characterized by correlation functions of speckle intensities before and after the
change. After their explicit expressions are introduced, applications for measurement of plant growth and an
extensometer are described. Digital holography provides 3-dimensional distributions of the correlation functions from
which new developments are opened such as noise suppression and simplification of optical systems.
X-ray phase nanotomography through ptychographic coherent lensless imaging
Show abstract
We describe experimental and algorithmic developments of ptychographic X-ray computed tomography, a recently
reported technique that enables three-dimensional, quantitative X-ray microscopy with high sensitivity. The
technique is based on the incorporation of sample rotation and tomographic reconstruction to scanning X-ray
diffraction microscopy (SXDM), a robust technique for two-dimensional X-ray coherent lensless imaging.
Biomedical Optics
Physics and agriculture: applied optics to plant fertilization and breeding
K. Diomandé,
P. A. Soro,
G. H. Zoro,
et al.
Show abstract
The economy of Côte d'Ivoire rests on the agriculture. In order to contribute to the development of this
agriculture, we have oriented our research field on applied optics to agriculture. Then, our research
concerns mainly the Laser Induced chlorophyll fluorescence in plants. A simple laser-induced
fluorescence set up has been designed and built at the Laboratory of Crystallography and Molecular
Physics (LaCPM) at the University of Cocody (Abidjan, COTE D'IVOIRE). With this home set up we
first have studied the fluorescence spectra of the "chlorophyll" to characterize the potassium deficiency
in oil palm (Elaeis guineensis Jacq,). However, we found that the results differed for samples along
terraced plots. The study of this phenomenon called "border effect", has enabled us to realize that
sampling should be done after two rows of safety in each plot. We also applied the Laser Induced
chlorophyll fluorescence technique to improve the plant breeding. For this, we have characterized the
rubber tree seedlings in nurseries. And so we have highlighted those sensible to drought and resistant
ones.
Gastric mucosa analysis using speckle patterns: a medical diagnosis alternative
Show abstract
Speckle techniques have been extensively employed in biomedical applications. It has been shown, that these non
invasive optical techniques are useful to discriminate healthy tissues from those presenting some type of pathology. In
this work we analyze speckle patterns from histological samples of gastric mucosa obtained by means of digestive
endoscopies with three different histopathological confirmed diagnoses: atrophy, metaplasia and dysplasia. We studied
biopsies from 27 patients and formed groups following the corresponding speckle contrast features. Three different
groups according to the speckle contrast were established: higher for intestinal metaplasia, intermediate for gastric
dysplasia and low for gastric atrophy. The comparison with histopathology shows a high value of concordance between
both tests, making this methodology emerges as a possible new classification system for qualitative and quantitative
gastric biopsy using optical techniques.
Whole field reflectance optical tomography
Nicolás A. Carbone,
Héctor A. García,
Héctor O. Di Rocco,
et al.
Show abstract
Optical imaging through highly scattering media such as biological tissues is a topic of intense research, especially for
biomedical applications. Diverse optical systems are currently under study and development for displaying the functional
imaging of the brain and for the detection of breast tumors. From the theoretical point of view, a suitable description of
light propagation in tissues involves the Radiative Transfer Equation, which considers the energetic aspects of light
propagation. However, this equation cannot be solved analytically in a closed form and the Diffusion Approximation is
normally used. Experimentally it is possible to use Transmission or Reflection geometries and Time Resolved,
Frequency Modulated or CW sources. Each configuration has specific advantages and drawbacks, depending on the
desired application. In the present contribution, we investigate the reflected light images registered by a CCD camera
when scattering and absorbing inhomogeneities are located at different depths inside turbid media. This configuration is
of particular interest for the detection and optical characterization of changes in blood flow in organs, as well as for the
detection and characterization of inclusions in those cases for which the transmission slab geometry is not well suited.
Images are properly normalized to the background intensity and allow analyzing relative large areas (typically 5 × 5 cm2)
of the tissue. We tested the proposal using Numerical Monte Carlo simulations implemented in a Graphic Processing
Unit (Video accelerating Card). Calculations are thus several orders of magnitude faster than those run in CPU.
Experimental results in phantoms are also given.
Multifocal nonlinear microscope with single element detector for multidepth imaging
Show abstract
We present a laser scanning microscope capable of producing multiple focal volumes. These volumes can be displaced
vertically, to acquire simultaneous images from multiple planes, or superimposed at the same depth but with different
polarization states. We call this last implementation, differential multiphoton laser scanning microscopy (dMPLSM). To
our knowledge, this constitutes the first report of a multifocal microscope with this capacity. The microscope is able to
take images in different modalities, two-photon excited fluorescence, second, and third harmonic generation. In this
work, we demonstrate several capabilities of our microscope: simultaneous acquisition of two and six images from two
focal planes separated by several microns, and a pair of simultaneous images taken at the same focal plane but with two
different polarizations. Some potential applications include following microorganism motion, studies of phase matching
in microscopic environments, studies of blood flow, etc. The microscope is based on a pulsed ultrafast laser. The pulses
are split, manipulated and recombined in an interlaced pattern in order to generate a sequence of pulses with different
divergences, and possibly different polarizations. This pulse train is sent to the objective and focused at different depths.
The signal is recorded using a photoncounting photomultiplier tube. Images from different foci are separated using time
demultiplexing based on a low cost field programmable gate array. The use of a single element detector, instead of a
multi-element (CCD camera), allows for imaging of scattering media. The use of photon counting leads to lower signal
to noise ratio in the images.
Determination of stereoisomer in sugars by THz-TDS
S. Yamauchi,
Y. Imai,
H. Yokota,
et al.
Show abstract
Transmission-type terahertz time-domain spectroscopy (THz-TDS) using dipole-antennas on LT-GaAs layers as THzemitter
and detector with fs-fiber laser as the excitation light source was applied to determine the stereoisomer of sugars
in carefully controlled environment with low humidity below 5% at 20°C. Commercially available α-D-lactose including
about 4% anomer and β-D-lactose including below 30% anomer were used as stereoisomer samples. The absorption
spectra of compounds by the α-D- and β-D-lactose powders with various ratios were successively deconvoluted to four
spectra by Lorentzian and dependent on the composition ratio. Integrated absorptions due to α-D-lactose and β-D-lactose
determined the decreasing rate (rα) and the increasing rate (rβ) for the composition ratio of the β-D-lactose powder,
because the intensities were linearly dependent on the composition ratio. The net-composition ratio of α-lactose and β-lactose in the compounds was precisely evaluated by the ratio of the integrated intensities and the value of rβ / rα, for
example, the anomer-contents in commercially available α-D-lactose and β-D-lactose powders were disclosed as 3.9%
and 29.1%, respectively. The demonstrated results indicate that THz-TDS is so useful not only for precise qualitativeanalysis
but also for precise quantitative-analysis of stereoisomer in sugars with partially different molecular structure
such as lactose.
Laser vibrometry for measurement of nonlinear distortions in the vibration of weakly nonlinear slowly time-varying systems
Johan R. M. Aerts,
Daniël De Greef,
John Peacock,
et al.
Show abstract
Recently, a new signal analysis method was developed to detect small non-linear distortions in weakly non-linear
systems using specially designed broadband excitation signals, i.e. odd random phase multisines. The method
allows the detection and quantification of the system response, noise level and both odd and even degree nonlinear
distortions over an extensive frequency range from one single short-term measurement. Here, this method
is implemented in an opto-acoustical set-up to detect small non-linearities in the response of vibrating structures.
Because of the highly linear response achievable with heterodyne vibrometry, it is possible to detect non-linearities
in the system under test with extremely high sensitivity. Non-linear behaviour is very common in biomechanical
systems, but their dynamics and thus response might change over time. This leads to measurement artifacts that
cause an overestimation of the noise level. A correction algorithm can be applied to remove the effect of these
time variations, so that heterodyne vibrometry also allows the detection and quantification of non-linearities
in unstable biomechanical systems. In this paper the technique is demonstrated with a measurement of the
non-linear distortions in the vibration of the gerbil middle ear, where the use of a non-contact optical detection
method is essential to not disturb the tiny vibrating structures.
Validation of a new algorithm for the recovery of optical properties from turbid samples: GA-MCML against IAD program
Show abstract
Determining optical properties of turbid media has been performed by many research groups using a technique
based on iteratively solving the radiative transport equation using the adding doubling technique (IAD). We
present a new, alternative method, GA-MCML, for determining optical properties based on a Monte Carlo tech-
nique for radiative transport (MCML) guided by a genetics algorithm. The Monte Carlo method is more
exible
than the adding-doubling technique and can be adapted to a wider range of sample geometries. The genetic
algorithm is a robust search technique that is well-adapted to avoiding the local minima in this optimization
problem. GA-MCML, has been implemented by modifying the MCML source code to account for two common
experimental problems: light losses due to the nite sample size and non-linear integrating sphere eects using
Mott's equations. GA-MCML was validated by comparing with IAD method for data acquired at 632.8 nm
on a set of phantoms using a single integrating sphere system. The GA-MCML results were equivalent to the
IAD technique.
Study of inhomogeneities in turbid media: experimental and numerical results
N. A. Carbone,
Héctor O. Di Rocco,
Daniela I. Iriarte,
et al.
Show abstract
Near Infrared diffuse transmission of light through tissue is a tool for noninvasive imaging for diagnostic purposes. Most
of the research has been focused over breast cancer imaging; however, major efforts have been done in cerebral
tomography and topography imaging, as well as small animal organs imaging systems. In this work, we investigate the
transmitted light profiles when scattering and absorbing cylindrical inhomogeneities are submerged at different depths
inside slabs of turbid media. We analyze the transilluminance profiles when the phantom is scanned using both, CW and
time resolved detection. The study of the spatial profiles obtained with CW light, shows an apparently contradictory
effect when the absorption coefficient of the inclusion is higher than that of the bulk. In this case, the intensity profiles
displays a peak of higher intensity where the inclusion is located, as it would be expected for a less absorbing inclusion.
The experiments were compared and analyzed with a theoretical model for cylindrical inclusions and Monte Carlo
simulations implemented in a Graphic Processing Unit (GPU).
Relationship between reflection spectra of breast adipose tissue with histologic grade
Show abstract
Optical spectroscopy allows the characterization, recognition and differentiation of subcutaneous tissues
healthy and no-healthy, to facilitate the diagnosis or early detection for breast cancer are studied white
adipose tissue by the subcutaneous region with the help of the diffuse reflection spectroscopy in the visible
areas (400 to 700 nm) of electromagnetic spectrum for them using a spectrometer portable of integrating
sphere, Hunter lab Model Mini-Scan. The problem to be solved for cancer detection by optical techniques is
to find the solution to the inverse problem of scattering of radiation in tissue where it is necessary to solve the
equation of energy transfer. us through the trigonometric interpolation and by the data adjustment by least
squares using Fourier series expansion to parameterize the spectral response curves of each sample of breast
adipose tissue then correlated with histological grades established by the optical biopsy for each one of the
samples, allowing use this technique to the study of anomalies in White Adipose Tissue Breast, changes are
evident in the spectral response for Breast Adipose Tissue carcinogens with respect to healthy tissues and for
the different histological grades.
Determination of coagulation time of human blood by biospeckle technique
Show abstract
When a lesion occurs in a blood vessel, a series of mechanisms are activated to stop hemorrhage by increasing blood
viscosity at the wounded place.
If a sample of blood extracted of the human body is illuminated with coherent light, a time varying speckle pattern is
observed. It is show high activity at the start and decreases with time until it finally stop.
The analysis of these patterns shows a degree of correlation between speckle activity and the temporal evolution of the
clot.
These preliminary results are promising for the continuation of studies aiming to the application of biospeckle techniques
to the analysis of coagulation times.
Low cost optoelectronic system for paint drying monitoring
Show abstract
In previous works we reported several speckle interferometry methods applied to analyze paint drying processes. In this
paper we present the development of a low cost optoelectronic system for monitoring the drying status of different types
of paints. The system is composed by a laser diode, a linear CCD sensor and a microcontroller.
One of the key points of the system is the algorithm that processes the speckle patterns produced by the laser beam
scattered from the paint. The temporal evolution of the speckle carries information of the paint status. The proposed
algorithm modifies one of its parameters to follow the speckle rate of change, allowing a real-time measurement of the
drying process.
The results obtained with this system are compared to the ones obtained by the method that measures the paint weight
loss in time, due to the solvent evaporation, and to the results from other methods that process the temporal evolution of
the speckle with different algorithms.
Optical coherence tomography image enhancement by using gold nanoparticles
Show abstract
Optical Coherence Tomography (OCT) is an imaging technique to get cross-sectional images with resolutions of a few
microns and deep penetration in tissue of some millimeters. For many years OCT has been applied to analyze different
human tissues like eyes, skin, teeth, urinary bladders, gastrointestinal, respiratory or genitourinary tracts and recently
breast cancer tissues have been studied. Many of these tissues are composed specially of lipids and collagen, proteins
which cause multiple light scattering (MLS) reducing significantly the optical depth and the contrast of OCT imaging. So,
one of the big challenges of this technique is to acquire images with good contrast. Gold nanoparticles (NPs) exhibit
interesting optical properties due to its plasmon resonance frequency. Optical absorbance is strong when gold NPs have
dimension under 50 nm, but over this size optical scattering becomes dominant. In this work we show the preliminary
results of the use of gold NPs as a contrast medium to enhance the OCT images quality. Our experimental results show
which type of particles (morphology and size) present the best enhancement in the region of 1325 nm which corresponds
to the central wavelength source excitation. All our experiments were carried out with a commercial OCT (thorlabs)
system and our NPs were tested in water and gel phantoms.
Fiber optic nanoprobes for biological sensing
Show abstract
Optical sensors have a large impact in the fields of life science research, drug discovery and medical diagnostics. The
recent advances in nanotechnology and photonics have led to a new generation of nanotools, capable of probing even the
single cell: it has already been demonstrated that nanobiosensors can detect biochemical targets and proteins inside living
single cells. Here we provide a brief overview of the field of nanoprobes consisting of tapered, metal-coated optical
fibers having nanosize tips, such as those which were originally developed for use in near-field optical microscopy.
Moreover we present some preliminary results concerning the characterization of the experimental sensing system which
exploits such nanoprobes for intracellular biomedical diagnostics. The feasibility of using the Fluorescence Lifetime
Imaging Microscopy (FLIM) technique as a dynamic diagnostics tool with these nanoprobes has been demonstrated.
Dual-beam laser Doppler vibrometer for measurement of pulse wave velocity in elastic vessels
Adriaan Campo,
Joris Dirckx
Show abstract
When a fluid flowing through an elastic vessel is subjected to a sudden change in pressure gradient, pressure pulses will
propagate through the fluid. Velocity of these pulse waves (PWV) can be determined by simultaneous detection of wall
distension on two separate points on the vessel wall, along its trajectory. PWV depends on wall stiffness, and under
certain circumstances, wall stiffness can be calculated from the propagation velocity. Optical interferometry is a noncontacting
technique that allows measurement of wall distension on discrete locations. In this work we propose a
miniaturized dual-beam laser Doppler vibrometer (LDV) to measure wall distension simultaneously at two locations.
Our dual-beam LDV is based on a single laser source and one acousto-optic modulator with as much as possible of the
interferometer optics shared among the different beams. The dual-beam LDV was used for simultaneous detection of
wall distension of several elastic vessels of different stiffness. We found that PWV as measured in elastic vessels agrees
well with theoretically expected values, and measurement precision is better than 5%. Moreover, the dual-beam LDV
performs almost as good as commercial systems for detection of PWV. The dual-beam LDV can have applications in
cardiovascular risk management. Stiffness of large arteries has a very good predictive value for cardiovascular disease
and overall mortality. This parameter can be estimated from arterial PWV. Current methods to measure arterial PWV
suffer from several shortcomings. A dual-beam LDV can offer substantial advantages over existing techniques.
Birefringence and deformation measurements in porcine corneas using Fourier domain OCT
Show abstract
A polarization sensitive Fourier domain optical coherence tomography system to measure the
birefringence response and the internal deformation of porcine corneas is presented. The optical
system uses polarized light to recover simultaneously the s and the p polarization states. A CMOS
camera records a fringe pattern which reconstructs the thickness of the porcine cornea. Combining
both p and s states a polarization retardation map is observed inside the tissue. The corneas are
deformed due a hydro static test which simulates different intra ocular pressure variations. Results
show simultaneously the thickness of the cornea, its birefringence response and its mechanical micro
deformation.
Resolution study of imaging in nanoparticle optical phantoms
Show abstract
We present results of resolution and optical characterization studies of silicon dioxide nanoparticle solutions. These
phantoms consist of spherical particles with a mean controlled diameter of 168 and 429 nm. The importance of this work
lies in using these solutions to develop phantoms with optical properties that closely match those of human breast tissue
at near-IR wavelengths, and also to compare different resolution criteria for imaging studies at these wavelengths.
Characterization involves illuminating the solution with a laser beam transmitted through a recipient of known width
containing the solution. Resulting intensity profiles from the light spot are measured as function of the detector position.
Measured intensity profiles were fitted to the calculated profiles obtained from diffusion theory, using the method of
images. Fitting results give us the absorption and transport scattering coefficients. These coefficients can be modified by
changing the particle concentration of the solution. We found that these coefficients are the same order of magnitude as
those of human tissue reported in published studies. The resolution study involves measuring the edge response function
(ERF) for a mask embedded on the nanoparticle solutions and fitting it to the calculated ERF, obtaining the resolution
for the Hebden, Sparrow and Bentzen criteria.
Optimal wavelength selection for noncontact reflection photoplethysmography
Show abstract
In this work, we obtain backscattered signals from human forehead for wavelengths from 380 to 980 nm. The results
reveal bands with strong pulsatile signals that carry useful information. We describe those bands as the most suitable
wavelengths in the visible and NIR regions from which heart and respiratory rate parameters can be derived using long
distance non-contact reflection photoplethysmography analysis. The latter results show the feasibility of a novel
technique for remotely detection of vital signs in humans. This technique, which may include morphological analysis or
maps of tissue oxygenation, is a further step to real non-invasive remote monitoring of patients.
Gold nanoparticles surface modification using BSA and cysteine
Show abstract
Metal nanometer-size particles show intriguing optical properties which depend on their shape, size and local
environment. For these reasons, these materials have received a lot of attention in different scientific areas, and several
applications can be found, for example: fabrication of bio-sensor, electronic devices, catalysis and new drugs. However,
in the case of biomedical applications, metallic nanoparticles need to satisfy several requirements: bio-compatibility,
stability and functionality. To satisfy these requirements, metallic nanoparticles need to be modified in their surfaces. In
this work we report the synthesis and the modification of gold nanoparticles (GNPs) surface. GNPs were fabricated
following the Turkevich's method, and the bio-conjugation (surface modification) was done using cysteine and bovine
serum albumin (BSA). Our results of Uv-vis spectroscopy show that BSA and cysteine permit to increase the stability of
GNPs in presence of NaCl, the stability is function of BSA concentration. Also to verify the bio-conjugation we used
Raman spectroscopy and gel electrophoresis.
Micro-joule, pico-second range, Yb3+-doped fibre laser for medical applications in acupuncture
Show abstract
The work described here is based on the optical design, simulation and on-going
implementation of a pulsed (Q-switch) Yb3+-doped, 1-um diffraction-limited fibre laser with pico-second,
10 micro-Joule-range energy pulses for producing the right energy pulses which could be of benefit for
patients who suffer chronic headache, photophobia, and even nausea which could is sometimes triggered
by a series of factors. The specific therapeutic effect known as acupunctural analgesia is the main
objective of this medium-term project. It is a simple design on which commercially available software
was employed for laser cavity design. Monte Carlo technique for skin light-transport, thermal diffusion
and the possible thermal de-naturalization optical study and prediction will also be included in the
presentation. Full optical characterization will be included and a complete set of recent results on the
laser-skin interaction and the so called moxi-bustion from the laser design will be extensively described.
Evaluation of autofocus measures for microscopy images of biopsy and cytology
Show abstract
An essential and indispensable component of automated microscopy is the automatic focusing system, which
determines the in-focus position of a given field of view by searching for the maximal of an autofocus function
over a range of z-axis positions. The autofocus function and its computation time are crucial to the accuracy
and efficiency of the system. In this paper, we analyze and evaluate fifteen autofocus algorithms for biopsy and
cytology microscopy images, ranging from the already well known methods to those proposed recently. Results
have shown that there is a trade-off between computational cost and accuracy. Finally, the error committed by
each of the algorithms is presented.
Application of a new high-speed magnetic deformable mirror for in-vivo retinal imaging
Show abstract
Nowadays in ophthalmologic practice several commercial instruments are available to image patient retinas in vivo.
Many modern fundus cameras and confocal scanning laser ophthalmoscopes allow acquisition of two dimensional en
face images of the retina with both back reflected as well as fluorescent light. Additionally, optical coherence
tomography systems allow non-invasive probing of three-dimensional retinal morphology. For all of these instruments
the available lateral resolution is limited by optical quality of the human eye used as the imaging objective. To improve
lateral resolution and achieve diffraction-limited imaging, adaptive optics (AO) can be implemented with any of these
imaging systems to correct both static and dynamic aberrations inherent in human eyes. Most of the wavefront correctors
used previously in AO systems have limited dynamic range and an insufficient number of actuators to achieve
diffraction-limited correction of most human eyes. Thus, additional corrections were necessary, either by trial lenses or
additional deformable mirrors (DMs). The UC Davis AO flood-illuminated fundus camera system described in this
paper has been previously used to acquire in vivo images of the photoreceptor mosaic and for psychophysical studies on
normal and diseased retinas. These results were acquired using a DM manufactured by Litton ITEK (DM109), which has
109 actuators arranged in a hexagonal array below a continuous front-surface mirror. It has an approximate surface
actuator stroke of ±2μm. Here we present results with a new hi-speed magnetic DM manufactured by ALPAO (DM97,
voice coil technology), which has 97 actuators and similar inter-actuator stroke (>3μm, mirror surface) but much higher
low-order aberration correction (defocus stroke of at least ±30μm) than the previous one. In this paper we report results
of testing performance of the ALPAO DM for the correction of human eye aberrations. Additionally changes made to
our AO flood illuminated system are presented along with images of the model eye retina and in-vivo human retina
acquired with this system.
Cross-talk analysis in arterial hemoglobin oxygen saturation measurements
Show abstract
Previously, we analyzed the classical theory for oxygen saturation in blood. We proposed a novel model to reduce noise
effects, and a methodology based on standard deviation oxygen saturation maps to select the optimal wavelength zones
to improve oximetry measurements. We evaluate the oxygen saturation measurement for different wavelength pairs in
the spectral range from 650 to 1050 nm looking for accurate saturation values. We perform a cross-talk analysis in
hemoglobin absorbance spectra in order to find out the optimum center wavelength for light sources of extended
spectrum like a led. We compare the oxygen saturation results obtained with different peak wavelengths considering the
cross-talk effect between oxy- and deoxy-hemoglobin signals.
Spectra acquisition software for clinical applications of the USB4000 spectrometer
Show abstract
The non-invasive clinic method of diffuse reflectance spectroscopy (DRS), for the diagnosis of human skin lesions
can be performed by using spectrometric devices together with fiber optics probes. However, the operation of
most of these devices commercially available is not specifically designed for clinical applications. As a result, the
commercial software and the optical hardware of these spectrometers are impractical when trying to conciliate the
requirements of a clinical procedure with their operation to perform the DRS for diagnosis purposes. Therefore,
the development of home-built acquisition software will impact in a more reliable and practical spectrometric
system for clinical environment. In this work is presented the development of an automation system that includes
both a user graphical interface and a control system that enable a more reliable and faster acquisition of clinical
spectra. The software features a voice control to perform the acquiring spectra process. The impact of this work
is mostly the use of available programming platforms to implement a preliminary spectra processing tool that
will lead to real-time acquisition of skin reflectance spectra of a given patient.
Comparative study of OCT and microscopy images: a scaling approach
Show abstract
In this study was made a comparison between the optical coherence tomography and microscope images. We obtain
images from different biological tissues, and from a designed epoxy phantom to analyze if the SR-OCT 930 can obtain
images similar to microscopy images. The result is that the OCT images and the microscopy images are similar. Also
developed a software to analyze the OCT images without distorting the structures in the image when the image is obtain
in different image sizes.
Optomechatronic prototype based on digital holographic interferometry aimed to the study of biological tissues
Show abstract
This paper presents the preliminary stages of the development of a compact optomechatronic prototype for the
characterization and study of biological tissues in full field of view. The system is based on the optical non invasive
technique known as digital holographic interferometry (DHI), which allows displacement measurements in the
micrometer range, a key feature for the study of biological tissues. An ad-hoc optomechanical design contemplates a
sturdy system yet compact that renders high quality images able to generate new data about the biological tissues under
study. These data contain quantitative and qualitative information of tissue mechanical parameters. The DHI results are
presented as fringe phase maps related to tissue surface displacements, showing that the proposed prototype provides non
invasive information pertaining to the mechanical characteristics of the tissue which can be used later to diagnose certain
tissue pathologies. The use of this prototype in the biomedical area may be thought of as a new and complementary tool
for the study and research in full field of view that may even be used in conditions outside the laboratory.
Vision and Colour
Optical phenomena in microprism diagnostic set KK-42
Show abstract
Microprism diagnostic set KK-42 for ophthalmology application comprises 42 separate microprism elements - strabismus optical compensators and it is designed for the image displacement at vision diagnostics.
The main requirement for optical compensators is high quality of observed images. However, strong diffraction
phenomena and chromatic aberrations due to light dispersion exist for microprisms similar to any other prismatic
systems. Structure simulation was carried out to minimize the acuity degradation and to avoid observed image
discretization. The simplest method to diminish aberrations is the application of filters and colour plastics. Experiments
and calculations were performed which showed the opportunity to diminish twice the chromatism zone by filters to the
value of 20-25 angular minutes.
Another method of decreasing chromatic aberrations is application of additional prism microrelief - saw tooth
diffractive optical element. In optical compensators the first microrelief with the pitch of 600-800 μm serves as a
refractive prism. Diffractive element with the pitch of 15-20 μm operating in first diffractive order is optimized in such a
way that dispersion of the first diffractive order compensates dispersion of the compensator. This method allows to
compensate dispersion totally at any spectrum zone.
Effect of cataracts on scattering of light in the eye
Ismael Kelly-Pérez,
Neil C. Bruce,
Luis R. Berriel-Valdos
Show abstract
We compare the radial profiles of light pattern distributions formed in the retina and the exit pupil of a computational
model eye, when the wavelength is varying. The computational eye simulates the presence of cataracts,
as a particle distribution in the lens. We use three different wavelengths (400, 550 and 700 nm) for the incident
light. The results show that for the shorter wavelength the effect of scattering is bigger around the center of the
images while for the longest wavelength the light distribution is larger in the edges of the images. The distance
from the center of the scattered light pattern to the zone where the profiles cross is inversely proportional to the
size of the particles.
A novel illumination-invariant colour constancy algorithm
L. A. Torres-Méndez,
M. L. Quiñones Muñoz,
E. J. Olaya-Benítez
Show abstract
The human brain is able to extract the colour of objects no matter the existing illumination conditions which
may affect the appearance of their colour. For a person, an object that is red, it will be red regardless of the
type of illumination source. However, for a computer algorithm to achieve the same task is not as simple. For
vision and robotics applications were feature extraction is essential having such an algorithm is crucial. It is
well known from the literature that the colour of an object does not only depend on the chemical composition
and shape of its surface but also on the illumination conditions, the intensity, number, location and colour of
the sources of illumination as well as the intrinsic and extrinsic characteristics of the sensor used. Based on that
knowledge, we propose a simple colour constancy algorithm that uses the quaternion representation of each pixel
in the image instead of the commonly used RGB model. We assume linearity in the reception of the luminance
spectrum of the charge-coupled device of the camera before variations in the illumination. We have tested our
colour constancy algorithm in a variety of images containing different colour objects under different illumination
conditions. Our experimental results show the feasibility of the proposed method.
Simple perceptual color space for color specification and real-time processing
Show abstract
In this work an alternative color space is described that defines the color elements in terms of approximated
brightness, hue and saturation, similar to other color spaces commonly used in computer applications. The
classical color spaces such as HSL and HSV in the form that is widely used are made for convenience, and
do not model colors based on human perception. Other classical color spaces such as CIELAB, DIN99 and
even more recent CIECAM-based color spaces are too cumbersome and difficult to work with. The proposed
alternative, on the other hand, is simple to work with and has its "lightness" component tuned up to represent
the perceived brightness closer to the reality. It is based on how luma is calculated in color spaces such as
YUV and YIQ among others, but instead of using constant coefficients, it uses Euclidean distance formula
with weighting coefficients.
Several experiments are described that illustrate the proposed color space visualized in 3D and compared to
other color spaces in perceptual terms and performance benchmarks. This is aided by a novel technique that
allows normalizing the chroma of existing color spaces within a fixed interval. The experiments show that the
proposed color space is a viable alternative for applications that already use HSV and HSL. A practical
application is described, where the color space is used for 3D illumination with specular reflections running on
dedicated graphics processor unit using shaders. This resolves visual defects present in the classical
approaches that use RGB color space.
Calibration of a multispectral camera system using interference filters
Show abstract
The present paper proposes a calibration method of a multispectral camera system using interference filters. A spectral
image processing is effective to acquire an inherent information of an object in a general way. However, filter
registration error often occurs when the interference filter is used. Therefore, a calibration method is presented for
correcting observed images. Moreover, we describe a method for digital archiving of oil paintings based the present
imaging system.
Objective performance of a set of uncorrected 20/20 normal eyes: clinical reference
Show abstract
In recent years we have been working in the characterization of the objective average performance of a set of
uncorrected human eyes with a 20/20 visual acuity, described as the resultant average wavefront aberration function
(WA), point-spread function (PSF), modulation transfer function (MTF), and power refractive maps. This objective
performance has been used as our clinical reference to analyze the objective pre- and post-operated performance in laser
refractive surgery in different situations. We show some of our current results obtained from the application of our
clinical reference.
Energy balance in apodized diffractive multifocal intaocular lenses
Show abstract
The energy distribution between the distance and near images formed in a model eye by three different apodized
diffractive multifocal intraocular lenses (IOLs) is experimentally determined in an optical bench. The model eye has an
artificial cornea with positive spherical aberration (SA) similar to human cornea. The level of SA upon the IOL, which is
pupil size dependent, is controlled using a Hartmann-Shack wave sensor. The energy of the distance and near images as
a function of the pupil size is experimentally obtained from image analysis. All three IOLs have the same base refractive
power (20D) but different designs (aspheric, spherical) and add powers (+4.0 D, +3.0 D). The results show that in all the
cases, the energy efficiency of the distance image decreases for large pupils, in contrast with the theoretical and
simulated results that only consider the diffractive profile of the lens. As for the near image, since the diffractive zone
responsible for the formation of this image has the same apodization factor in the spherical and aspheric lenses and the
apertures involved are small (and so the level of SA), the results turn out to be similar for all the three IOL designs.
Dynamic point shifting in null screen videokeratometry
Show abstract
For obtaining the shape of the corneal surface through the Null Screen method, a numeric integration procedure must be
carried out; perhaps, the simplest integration method is the trapezoid rule. This method, however, is limited by the
truncation error. It has been shown previously [1-6] that the point shifting method allows the reduction of this error by
adding many more evaluation points so reducing the average spacing between evaluation points. To do so, an array of
LCD's must be used to display the moving Null Screen. In this paper we propose to use three LCD forming a triangular
prism, instead of a cylindrical Null Screen [3] for measuring the shape of the human corneas. The null screen design will
be described and some experimental results obtained with calibration spheres used to simulate the corneal surface will be
presented.
New trends in intraocular lens imaging
Show abstract
As a result of modern technological advances, cataract surgery can be seen as not only a rehabilitative operation, but a
customized procedure to compensate for important sources of image degradation in the visual system of a patient, such
as defocus and some aberrations. With the development of new materials, instruments and surgical techniques in
ophthalmology, great progress has been achieved in the imaging capability of a pseudophakic eye implanted with an
intraocular lens (IOL). From the very beginning, optical design has played an essential role in this progress. New IOL
designs need, on the one hand, theoretical eye models able to predict optical imaging performance and on the other hand,
testing methods, verification through in vitro and in vivo measurements, and clinical validation. The implant of an IOL
requires a precise biometry of the eye, a prior calculation from physiological data, and an accurate position inside the
eye. Otherwise, the effects of IOL calculation errors or misplacements degrade the image very quickly. The
incorporation of wavefront aberrometry into clinical ophthalmology practice has motivated new designs of IOLs to
compensate for high order aberrations in some extent. Thus, for instance, IOLs with an aspheric design have the potential
to improve optical performance and contrast sensitivity by reducing the positive spherical aberration of human cornea.
Monofocal IOLs cause a complete loss of accommodation that requires further correction for either distance or near
vision. Multifocal IOLs address this limitation using the principle of simultaneous vision. Some multifocal IOLs include
a diffractive zone that covers the aperture in part or totally. Reduced image contrast and undesired visual phenomena,
such as halos and glare, have been associated to the performance of multifocal IOLs. Based on a different principle,
accommodating IOLs rely on the effort of the ciliary body to increase the effective power of the optical system of the eye
in near vision. Finally, we present a theoretical approach that considers the modification of less conventional ocular
parameters to compensate for possible refractive errors after the IOL implant.
Tangential and sagittal curvature from the normals computed by the null screen method in corneal topography
Show abstract
A new method for computing the tangential and sagittal curvatures from the normals to a cornea is proposed.
The normals are obtained through a Null Screen method from the coordinates of the drops shaped spots at
the null screen, the coordinates on a reference approximating surface and the centroids on the image plane.
This method assumes that the cornea has rotational symmetry and our derivations will be carried out in the
meridional plane that contains the symmetry axis. Experimental results are shown for a calibration spherical
surface, using cylindrical null screens with radial point arrays.
A review of adaptive optics in vision science
Show abstract
In this paper I briefly survey how adaptive optics is used in vision science to improve vision, carry out experiments in
visual perception, and to assist imaging the retina. In the coming years one can expect that more systems for vision
simulation and retinal imaging using adaptive optics will become commercially available.
Nanotechnology and Optics
Design and fabrication of reconfigurable metamaterial devices using MEMS
Show abstract
This work presents the design, fabrication and characterization of Metamaterial (MTM) structures using MEMS
technology for applications in bio-medical optics. Metamaterials can be applied in diverse fields such as Photonic
Crystals, Resonant Structures and Transmission Lines. In this work the focus is on Transmission Lines. For this
application, the metamaterial structure is based on a Composite Right/Left Handed Transmission Line (CRLH-TL)
which consists of MEMS capacitors and inductors. The MEMS capacitor is formed with two parallel plates (two
electrodes, one mobile-positive and one fixed-negative), whose capacitance can be varied using electrostatic principles;
in addition it acts as a 3D element for metamaterial device tuning.
Artificial apposition compound eye using aspherical cylindrical micro-doublets
Show abstract
An ultrathin objective with the configuration of an artificial apposition compound eye was
designed in order to obtain a miniaturized camera. The optical design was based in a nonconventional
multi aperture configuration of a diurnal insect eye that uses ommatidia as
individual units. An aspherical cylindrical micro doublet (CMD), obtained by ALSIE, is
used in this optical design to improve the image quality in more than 200 percent in
comparison with the first design with the spherical CMD.
Study of soliton self-compression in photonic nanowires
Show abstract
Waveguides with sub-wavelength dimensions known as photonic nanowires are among the most attractive optical
structures for ultrafast nonlinear optics. They provide high nonlinearities and allow the generation of cyclical temporal
compression and broadband supercontinuum in few millimeters length. In this work, we numerically investigate the
soliton self-compression in photonic nanowires fabricated by tapering standard single mode fibers. We demonstrate, the
generation of 1.53 fs compressed pulse (ca. 0.57 single optical cycle) from 100 fs input pulse by pumping at low input
pulse energy of 2.5 nJ, a 1.15 mm-long nanowire with a diameter of 800 nm. Thus, broadband supercontinuum spanning
from 260 nm to 1800 nm is generated. Air-silica nanowires present very promising coherent white-light sources and
ideal waveguides for nonlinear applications such as single-cycle pulses generation and optical processing.
Applied Optics to Artwork
Xochicalco: Tlayohualchieliztli or camera obscura
Show abstract
Xochicalco is an archaeological site located in the state of Morelos in central Mexico. It flourished from 600 to 900 a.d. with numerous multicultural elements. There are several underground rooms carved into the hillside In particular, a room with a shaft that has a hole in the roof whose orientation towards the zenith supports its astronomical purpose. Our hypothesis is that the place was used as a tlayohualchieliztli or camera obscura for astronomical observations. This would be the first evidence of a pre-columbian image forming device. To explore the feasibility of this assertion, the conditions required to produce an image were studied. The aperture diameter in the top of the shaft is far too large to be used as a "pinhole" but it may have been covered with a screen containing a smaller bore-hole. We work out the optimum aperture size. The portion of the sky that could be observed due to the orientation of the shaft was also undertaken. The two most intense celestial objects should produce bright enough images thus suggesting that observation of the sun took place during day-time and observation of the moon during night-time. Amate paper or cloth could have been used to directly draw the position of celestial objects.
Numerical reconstruction of spectral reflectance curves of oil painting on canvas
Show abstract
Unlike the color -which is a quality without physical meaning and that involves subjective estimation of interaction of
electromagnetic radiation with surfaces- spectral reflectance is a physical property that characterizes different materials,
no matter what chromatic content of illuminant and the spectral response of the sensor. This means that the spectral
reflectance is a magnitude of particular interes in both reconstruction and reproduction in digital color systems.
In this paper, two approaches to the numerical reconstruction of spectral reflectance curves of samples of oil painting on
canvas, are presented. These approaches need a set of spectral reflectance curves, given by a spectrophotometer, and
their respective sampling using color filters placed in front of a monochrome CCD camera.
The first approach is based on the interpolation of the camera response to each color filter. The second one, relies in
obtain a vectorial base and appropiate coefficients to reconstruct the spectral reflectance curve. Goodness of fit
coefficient (GFC) and absolute mean error (ABE) are the metrics used to evaluate the performance of the proposed
procedures.
Science and Society
Wordwide scientific collaboration and national intellectual property: How to put those things together?
Show abstract
In this paper we made an attempt to discuss some important questions of intellectual property in international
collaboration between scientists. Global nature of the scientific research is a nowadays reality, while IP laws still
have national character. Though the basic principles of IP protection are similar in all countries, there are certain
differences in legislation, and it affects the collaboration. Since the material is presented at World Congress on
Optics, we describe it on example from optical sciences.
Optical Engineering Post Deadline Paper
Digital image correlation method: a versatile tool for engineering and art structures investigations
Show abstract
Optics as the enabling technology is applied in many applications of engineering, medicine, multimedia and conservation
of cultural heritage. Most of these applications require close cooperation with the end user and often they enforce
modification and enhancement of an optical tool. In the paper we show how optical metrology, specifically the
application of digital image correlation method is implemented to two completely different tasks: performing preoperating
tests of low cost building structures subjected to loading conditions which simulate the natural load e.g.
introduced by the weight of snow and monitoring of canvas paintings for tracking humidity-induced deformations,
which may appear in museum (or other location of a piece of art e.g. church).
The presented examples are the background for a general discussion on different measurement scenarios with application
of DIC method, as well as the required enhancements and modifications which have been introduced.