InGaN-based LEDs and laser diodes
Author(s):
Shuji Nakamura
Show Abstract
A violet InGaN multi-quantum well/GaN/AlGaN separate- confinement-heterostructure laser diode (LD) was grown on epitaxially laterally overgrown GaN on sapphire. The threshold current density was 2 - 4 kA/cm2. The LDs with cleaved mirror facets showed an output power as high as 30 mW under room-temperature continuous-wave (CW) operation. The stable fundamental transverse mode in the near-field patterns was observed at an output power up to 30 mW. The lifetime of the LDs at a constant output power of 5 mW was more than 1,900 hours under CW operation at an ambient temperature of 50 degree(s)C.
Design of an achromatic Fourier system by means of Wigner algebra
Author(s):
Adolf W. Lohmann;
Dayong Wang;
Avi Pe'er;
Asher A. Friesem
Show Abstract
An achromatic Fourier system (AFS) performs optically a Fourier transformation in spatially coherent white light, without color blurring. Our design method uses matrix algebra, applied upon the Wigner distribution function. The matrix procedure is similar to what is used in geometrical objects. However, our approach is valid also for wave optics. That is important because the AFS does contain not only refractive lenses, but also diffractive lenses (Fresnel zone plates).
Optimal 3D beam forming
Author(s):
Gal Shabtay;
Uriel Levy;
David Mendlovic;
Zeev Zalevsky;
Emanuel Marom
Show Abstract
A beam propagating in free space is exposed to the laws of diffraction, which tend to deform the wave front. Hence, 3D beam forming is a very applicable task. For instance it may be useful in designing a special beam to be used for scanning purposes, beam forming for optical communication modules and 3D beam forming as a tool to exceed system's resolving power. There are several techniques, which allow obtaining a reduced sensitivity to diffraction in a pre- determined region of propagation. In this paper a novel optimal technique is suggested. Using the calculus of variation method we derive an analytic expression for an optimal filter in the mean square error sense, to obtain a 3D beam forming, which is as close as possible to the desired 3D distribution. We applied the proposed method for obtaining a scanning beam with improved performances. The suggested approach was tested in computer simulations as well as in optical experiments and was proven to deliver improved performance. Thus one can obtain an extended working region using the resulting beam with confined lateral spread.
Chromatic compensation of light diffraction: novel broadband diffraction-based applications
Author(s):
Pedro Andres;
Vicent Climent
Show Abstract
Different optical architectures designed for compensating the chromatic dispersion inherent to free-space broadband light diffraction are presented. These devices are formed by a small number of conventional refractive objectives and diffractive lenses. In a second stage, several achromatic diffraction-based information processing techniques working with spatially-coherent or spatially-incoherent white-light illumination are also discussed.
Electromagnetic wavelet propagation and diffraction
Author(s):
Yunlong Sheng;
Sylvain Dechenes
Show Abstract
For the first time we show that optical diffraction is a wavelet transform with the electromagnetic wavelets, which are reduced to Hyugens' wavelets by a temporal. Fourier analysis in the case of monochromatic field. We define the non-diffracting electromagnetic wavelet by integrating a subset of the electromagnetic wavelets. A non-diffracting field can be constructed by a linear combination of the non- diffracting electromagnetic wavelets, which are the one-side windowed Fourier transform of the Bessel beams with a temporal frequency window and are spatially localized in the lateral direction, translated in the propagation direction and scaled in the time and the temporal frequency.
Telescopes with dynamic nonlinear-optical correction for distortions
Author(s):
Vladimir A. Berenberg;
Alexey Leshchev;
Michael V. Vasil'ev;
Vladimir Yu. Venediktov
Show Abstract
The paper describes the decade history and the recent advances in the field of the telescopes, where the nonlinear-optical effects are used for the correction for image distortions, caused by the defects and deformations of the primary mirror and of some other elements. Described are the schemes, based on phase conjugation use, which can work with the coherent radiation (beam direction, laser collimators and imaging with coherent illumination) and the schemes, based on the use of the dynamic holography, applicable to the remote objects (astronomy, Earth observation) in the incoherent radiation with the wide spectrum.
Progress in atmospheric adaptive optics
Author(s):
Robert Q. Fugate
Show Abstract
Significant advances have been made in the development and performance of large scale adaptive optical systems in recent years. Technological innovations in sensors, processors, wave front correctors, and laser guide stars have all contributed to the rapid growth of adaptive optics as an enabling technology for ground based optical astronomy in the 21st century.
Large optical switches
Author(s):
Robert Ian MacDonald
Show Abstract
Capacity growth in networks requires optical crossconnect switches that can be assembled incrementally, probably to large ultimate sizes, preferably using identical submodules of small size. Continued strict-sense nonblocking operation must be ensured during expansion, and expandability should have minimal impact on the initial cost. Large ultimate sizes mandate multistage architectures which impose difficulties in the expansion. We discuss the design of optical switching matrices for > 100 X 100 ports using a new modular multistage architecture that focusses on expandability.
Novel efficient wavelength assignment algorithm for bidirectional WDM rings
Author(s):
Nina L. Taranenko;
Martin C. Nuss;
Anthony L. Lentine
Show Abstract
Ring networks are the architecture of choice for WDM (Wavelength Division Multiplexing) telecommunication networks because of their inherent survivability, scalability, and large capacity. We describe a novel and efficient algorithm that allows a substantial reduction of the number of wavelengths required for full interconnection of bidirectional WDM ring, yet has much simpler wavelength assignment than the precisely optimal algorithm.
Limits of dense WDM
Author(s):
Andrew R. Chraplyvy
Show Abstract
The widespread introduction of erbium-doped fiber amplifiers in lightwave transmission systems has ushered in the WDM (wavelength-division multiplexing) era. Early WDM systems (five years ago) transmitted eight 2.5 Gb/schannels spaced by 200 GHz. In the coming year lightwave systems with 160 channels each at 10 Gb/s spaced by only 50 GHz will be introduced. Such high-capacity systems are plagued by optical nonlinearities in the transmission fibers. Silica fibers exhibit a wide variety of optical nonlinearities that can be grouped into two categories, stimulated scattering and nonlinear refractive index effects. Stimulated scattering processes, such as Brillouin and Raman, cause wavelength conversion of signals, unwanted noise, crosstalk, and power depletion. The nonlinear refractive index of silica is the source of such effects as self-phase modulation (SPM), cross-phase modulation (CPM) and four-photon mixing (FPM). 5PM and CPM produce spectral broadening, pulse distortion, and timing jitter. FPM generates mixing products that can coherently interfere with the signals. An arsenal of techniques has been developed to mitigate the effects of these nonlinearities and this has led to the staggering increase in fiber transmission capacity. This talk will provide an overview of optical nonlinearities in fibers and some of the techniques designed to circumvent them
Rigorous solution of scattering by randomly rough surfaces: recent contributions to open problems
Author(s):
Marc Saillard;
G. Soriano
Show Abstract
In this paper, we address some of the most difficult problems encountered in surface scattering. The first part is devoted to our recent work about the rigorous solution for 2D metallic surfaces. An impedance approximation has been implemented to take into account the finite conductivity of the metals, and, to deal with surfaces of arbitrary size, the beam simulation method has been generalized. But still, several problems cannot be rigorously solved in three dimensions. One of them concerns shallow metallic surfaces in optics: how taking accurately into account the propagation of surface polaritons? A second challenge consists in solving a surface scattering problem under grazing incidence. Since the field on the surface spreads out in both problems, the same answer holds. The surface current is described in the Fourier space, while the sampling of the rigorous integral equation is still achieved in the coordinate space. The number of unknowns is drastically reduced, and standard forward solvers can be used. The last problem studied here is a step towards the inverse problem. What kind of geometrical parameter describing the surface can be extracted from intensity measurements in the far field? For multi-scale rough surfaces, we show that the wavelet correlation dimension is a good candidate for such a characterization.
Three-dimensional diffraction tomography by two-dimensional sectioning
Author(s):
Oyvind R. Halse;
Jakob J. Stamnes
Show Abstract
The hybrid filtered backpropagation algorithm of diffraction tomography is known to give good reconstructions of 2D objects with a low contrast relative to the background medium. Here we show how the method can be extended (1) to reconstruct objects with rather large contrasts, and (2) to reconstruct 3D objects.
Fractional Fourier transform in information optics
Author(s):
David Mendlovic;
Haldun M. Ozaktas
Show Abstract
The Fourier transform is one of the most important concepts in optical signal processing, and in the mathematical theory of signals and systems. It can be implemented optically as well as digitally, and constitutes the building block of more complex information processing operations. The fractional Fourier transform is a generalization of the ordinary Fourier transform and also has efficient digital and optical implementations. However, the fractional order parameter associated with the fractional Fourier transform makes it more versatile than the ordinary Fourier transform, leading to many applications in optics and signal processing.
Fractional moments for determining intensity PDFs from experimental data in atmospheric optical scintillation
Author(s):
Anna Consortini;
Florence Rigal;
Claudia Innocenti
Show Abstract
Non-stationarity of atmospheric turbulence gives rise to some practical problems when one wants to determine the probability density function (PDF) of intensity fluctuations from laser atmospheric propagation experimental data. For strong fluctuations, the number of uncorrelated data that can be collected in stationary conditions is generally not enough to correctly evaluate intensity moments of order greater than two 1} . In the case of very strong fluctuations even the second order moment (and also variance) can not be estimated with accuracy [2] This is due to the fact that the stronger the fluctuations the longer is the tail of the distribution, which represents the main contribution in high order moment evaluation. If only integer moments are considered, information about intensity PDF that can be extracted from its moments is thus very poor because only a few of them are correctly estimated
Experimental evidence of the effects of non-Kolmogorov turbulence and anisotropy of turbulence
Author(s):
Mikhail S. Belen'kii;
Stephen J. Karis;
Christina L. Osmon;
James M. Brown II;
Robert Q. Fugate
Show Abstract
We have observed experimental evidence of the effects of non-Kolmogorov turbulence (NKT) on wavefront tilt. In addition, we have observed the anisotropy of the horizontal and vertical tilt components caused by the anisotropy of turbulence near the telescope. We developed an experimental method, which allowed us to eliminate telescope vibration and isolate the atmospheric tilt from the star Polaris. The spatial and temporal statistics of the wavefront tilt were determined by using aperture masks having diameters in the range from 0.1 m up to 3.5 m. The measured dependencies of the tilt variance on the aperture diameter deviate from the prediction based on the Kolmogorov model. These dependencies have a knee, where the tilt variance approaches a constant level determined by NKT. Anisotropy was observed when comparing the X and Y components of wavefront tilt. On average the horizontal outer scale of turbulence estimated from the tilt statistics is larger than the vertical one by a factor of 2-3. Local topographical features and the telescope dome affect the outer scale with the result that the outer scale measured at the 1 .5 m telescope is smaller than that at the 3 .5 m telescope. The tilt power spectra have a ç2/3 andf"3 behavior in the intermediate and high frequency range, respectively, which is predicted by the Kolmogorov model. In the low frequency range, the spectra do not obey the prediction of existing theoretical models. In this range the power spectra of the horizontal tilt exceed that for vertical tilt as a consequence of anisotropy of turbulence. The tilt temporal correlation scale increases with increasing aperture size. For the large apertures the tilt correlation scale is ofthe order of a few seconds.
Astronomical applications of volume-phase holographic gratings
Author(s):
Samuel Charles Barden;
James A. Arns;
Willis S. Colburn
Show Abstract
Volume-Phase Holographic (VPH) gratings provide unique capabilities over classical surface gratings which can be exploited in modern astronomical spectrographs. The peak diffraction efficiency of a VPH grating is tunable due to the nature of Bragg diffraction. This allows a single dispersing element to serve the function of several classical gratings. Additionally, VPH grating structures can be stacked to produce complex gratings capable of directing the diffracted light in ways that classical gratings can not.
Active micromirror: a new adaptive optical microcomponent
Author(s):
Gilles Robert;
A. Coville;
L. Babadjian;
Serge Spirkovitch
Show Abstract
The AMM is a new kind of micromachined deformable mirror. It is a silicon mirror which can be electrostatically actuated by electrodes located on each side of the mirror. In this article we describe the characteristics and the results of modelization and testing of our deformable micro mirror.
Adaptive optics in China
Author(s):
Wenhan Jiang;
Ning Ling
Show Abstract
Adaptive Optical (AO) technology can compensate wave-front error by real-time sensing, controlling, and correcting to improve image and beam quality. The research and development on AO in China began in 1979. In 1980, the first laboratory on AO in China was established in the institute of Optics and Electronics (IOE), Chinese Academy of Sciences (CAS). The main activities of developing AO systems are conducted in this Institute with collaboration of other institutions. Since then several AO systems have been built in this Laboratory. Table I summarized the characteristics of these systems.
Photonic crystal fibers, waveguides, and resonators
Author(s):
Philip St.J. Russell;
J. C. Knight;
Timothy A. Birks
Show Abstract
Fibers and planar waveguides made from dielectric materials which are periodically patterned on the scale of the optical wavelength--photonic crystals--have quite remarkable properties, requiring a complete realignment of the goal- posts in conventional guided-wave photonics. For example, photonic crystal fibers can be designed to be single-mode at every frequency, and full 2D photonic bandgaps can permit light to be guided--single mode--in a core region where the refractive index is lower than the cladding. A whole menagerie of new possibilities are presently emerging, including hollow-core single-mode optical fibers and ultra- compact micro-components formed in planar photonic crystal films.
Inverse focal shift in truncated cylindrical waves
Author(s):
Carlos J. Zapata-Rodriguez;
Manuel Martinez-Corral;
Pedro Andres;
Amparo Pons Marti
Show Abstract
We report on a general analytical procedure to analyze the axial focusing properties of uniform cylindrical waves truncated by a rectangular window. The resulting on axis diffraction pattern explicitly depends on the square of the window height-to-width ratio. Depending on the value of this parameter, different kinds of axial behavior are observed. In particular, it is found that for low values of this parameter and low Fresnel number, an inverse focal-shift phenomenon can appear.
Imaging of (sub-) wavelength sized objects
Author(s):
Rene Daendliker;
Peter Blattner;
Hans Peter Herzig
Show Abstract
The objective of this paper is to show different aspects of the interaction of light with wavelength sized optical microstructures, and their imaging. Furthermore, we outline that a microoptical structure can generate a laminar or a turbulent optical field.
Applications of nondiffracting beams
Author(s):
Zsolt Bor;
Miklos Erdelyi;
Zoltan L. Horvath;
Gabor Szabo;
Karoly Osvay;
William L. Wilson Jr.;
Frank K. Tittel
Show Abstract
Non-diffracting beams represent a group of fields whose radial intensity distributions do not change during their propagation. In 1987 Durnin" showed that the field described by E(r, z, t) = A . Jo(k1r) . ei11t) (1) is an exact solution of the wave equation, where k + k = w2/c2, and J0 is the zero order Bessel function of the first kind. The field described by Eq. (1) represents a non-diffracting beam because the transverse intensity distribution is independent of the propagation distance (z). However, such an ideal beam cannot be realized experimentally over large values of z and r, since this would represent a beam with infinite energy and spatial extent. In the last twelve years several experimental arrangements have been proposed21 to create nearly non-diffracting Bessel beams and apply them in different domains of physics. In 1997 a new approach was suggested by the authors [3,4J for enhancing both the critical dimension (CD) and depth of focus (DOF) in optical microlithography based on Bessel beams. A Fabry-Perot etalon placed between the mask and the projection lens creates multiple images of the original mask pattern along the optical axis. The distance and the exact phase between these virtual images can be controlled by the separation of the etalon mirrors. The projection lens produces perfect images of the virtual mask patterns, shifted in position along the optical axis, in contrast with the conventional projection process, which produces a single image at the wafer surface. Preliminary theoretical and experimantal results showed that an etalon with optimized mirror separation is capable of enhancing the CD and DOF by 60% and 400%, respectively, using a single on-axis contact hole. In order to evaluate this technique for more complex, and realistic extended mask patterns, a microlithographic simulation tool must be employed. This software, however, is not configured in such a way that it can be immediately adapted to simulate the Fabry-Perot approach. An elegant and efficient method to model this Fabry-Perot technique is to represent the effect of the etalon with an appropriate pupil-plane filter. Such filters with a complex amplitude-phase transmission can be easily implemented in any simulation tool. In this work Prolith/2, a commercially available simulation software, was used to evaluate the aerial image of contact hole arrays and line-space patterns with different pitch sizes. Figure 1 depicts a typical 2D intensity distribution for an off-set hole array with and without filter. The resolution enhanced by 25%, while the filter shifted the optimum focal position by 5 microns towards the lens. Due to constructive interference between the diffraction rings, secondary maxima appeared between the main peaks. These peaks can be eliminated by means of controlling the spatial coherence of the illumination, or using a phase shifting mask that introduces a r phase difference between the adjacent holes. The filter with a narrow bandwidth introduces a pitch sensitivity and light loss into the system. A pattern can be imaged if the filter transmits the cardinal spatial Fourier components of the mask patterns. Missing components degrade the image quality. Application of such filters requires a complex optimization process that contains the evaluation of light loss, pitch sensitivity, and technical feasibility.
Partially coherent nondiffracting beams
Author(s):
Andrei V. Shchegrov
Show Abstract
We describe exact representations for partially coherent beams whose spectral degree of coherence remains invariant on propagation. Such beams are obtained by taking a random superposition of well-known coherent Bessel beams, each of which propagates without spreading in the transverse direction. The invariance in coherent properties for such partially coherent beams holds for propagation distances as large as the propagation distances of coherent Bessel beams.
Recent developments in hybrid mirror technology for the next-generation space telescope
Author(s):
Kelly J. Dodson;
Gregory V. Mehle;
Eldon P. Kasl
Show Abstract
The objective of this paper is to report the recent developments in lightweight mirror technology at Composite Optics, Incorporated. The developments are a result of the activities being conducted in support of the Next Generation Space Telescope Program. The sponsors of these efforts are the NASA Marshall and Goddard Space Flight Centers. The requirements, design approach, performance, and the technology status for the program are summarized.
Ultralightweight actively controlled mirrors for space
Author(s):
James H. Burge
Show Abstract
Advanced technology mirrors for large space telescopes are being developed that use thin facesheets controlled by actuators. This concept was proven with a 50 cm prototype and is now being implemented for a 2-m cryogenic mirror that weighs only 40 kg.
Final design of the active positioning actuators for the Large Binocular Telescope primary mirrors
Author(s):
Luciano Miglietta;
Valdemaro Biliotti;
Matteo Accardo;
Paolo Stefanini;
Bernardo Bettini;
Claudio Braccesi
Show Abstract
The latest generation of astronomical telescopes is equipped by primary mirrors about 8 meter in diameter increasing demands not only of the general mechanical structure but also of the technical performances of the mirror support systems. The Large Binocular Telescope has two 8.4 meter primary mirrors supported on the same elevation mechanical structure and, each of them, located in a mirror cell enviroment. Into the latter structures hundredth of pneumatic actuators bear the weigth of the primary mirror and six positioning actuators find out the six degrees of freedom of the mirror itself, then a new control system is able to determine realtime the stiffness and the damping required by the primary mirror system. In this paper the authors describe the mechanical and the electronic active control system design and testing of the position actuator prototype that mechanically link the 8.4 m honeycomb mirror to six rigidly reinforced locations on each primary Mirror Cell structure. During telescope operation, the adjustable length of the actuators precisely control the six degrees of freedom of the mirror. Each actuator has a high mechanical axial stiffness and, as new feature, an active control system, based on piezoelectric elements and capacitive sensor, in order to control the axial stiffness versus damping, with a bandwidth from DC up to 50 Hz, assuring that the natural frequencies of the mirror do not degrade the optical performance of the telescope under external forces as the wind spectrum. Moreover, other requirements have been satisfied in the mechanic of the actuators: flexures are provided to minimize any moments applied to the attachment of the actuator to the mirror; one axial load cell for each actuator provides a precise realtime measurement of the external forces applied to the mirror, such as wind loads, to feedback the pneumatic force system that supports the weight of the mirror; a very sensitive and precise capacitive sensor measures the total length of the actuator to submicron resolution upon request. Last but not least each actuator has a reliable fail-safe system that limits the compressive and tensile forces that can be applied to the mirror. The mechanical and the electronic design DSP based and all the experimental tests of this actuator prototype have been performed in the Astrophysical Observatory of Arcetri laboratories under the supervision of the authors of this paper.
Liquid mirror telescope applications
Author(s):
Ralph F. Wuerker
Show Abstract
The advent of inexpensive large aperature near diffraction limited Liquid Mirror Telescopes (LMT's) makes possible applications not sensitive to their near vertical viewing nature; such as, astronomical surveys, space debris surveys, lidar collectors, and laser radiation concentrators, for plasma creation experiments in the sky. LMTs are easily an order of magnitude less expensive than a polished glass reflectors, which are only approximations to the naturally perfect parabolic surtace created by a rotating liquid. Highly reflecting liquid mercury is easily cleaned and safe when handled correctly.
Large Binocular Telescope
Author(s):
Piero Salinari
Show Abstract
The Lange Binocular Telescope (LBT) Project is an international collaboration among US, German and Italian Astronomical Institutes to build a binocular telescope with two 8.4 m primary mirrors. The LBT will have a collecting area equivalent to that of a 1 1 .8 m single dish telescope, and an angular resolution, when the two mirror are co-phased, equivalent to that of a 22.8 m telescope. The construction of the Large Binocular Telescope is in progress on all aspects. The first of the two honeycomb primary mirrors is being prepared for polishing, while the preparation of the casting of the blank for mirror two is in progress at the Mirror Lab of the University of Arizona. The structure of the enclosure is completed on Mt. Graham (AZ) and telescope pre-erection is about to start in the Ansaldo factory in Milan (Italy). Operations will start in 2002 with one of the two primary mirrors while the telescope will operate with both mirrors from 2004. The initial instrumentation will consist of four types of instruments: - twin optical spectrograph located at the direct Gregorian foci, - twin wide field optical imagers at the prime foci, - twin near infrared spectrograph/imagers at the front bent Gregorian foci, - two different interferometers, one for optical and MR wavelengths and one for near/mid infrared at the central combined foci. The twin infrared instruments and the interferometers will be designed to fully exploit the adaptive correction provided by the adaptive secondary mirrors of the telescope.
Acousto-optic filters for fiber systems
Author(s):
Byoung Yoon Kim
Show Abstract
Basic principles and several key applications of wavelength tunable acousto-optic filters are described. The devices utilize periodic coupling of guided and/or dissipating modes in optical fibers provided by traveling acoustic wave in the same fiber. The wavelength tuning is realized by tuning the applied acoustic frequency, and proper phase matching condition selects filtered optical wavelength. Application of the acousto-optic filters to gain flattening of fiber amplifiers, wavelength selection, optical switching, and non-reciprocal filtering will be discussed.
GaAs/AlGaAs narrow-bandwidth in-line fiber filter
Author(s):
Erji Mao;
Christopher W. Coldren;
James S. Harris Jr.;
Diego R. Yankelevich;
Olav Solgaard;
Andre Knoesen
Show Abstract
A GaAs/AlGaAs in-line fiber optic filter for wavelength division multiplexing applications is demonstrated. The device consists of a GaAs/AlGaAs anti-resonant reflecting optical waveguide (ARROW) evanescently coupled to a single mode fiber. At certain discrete wavelengths, light is coupled from the fiber to the ARROW, due to phasematching conditions. Sharp resonances are observed around the design wavelength of 830 nm. The 3 dB cutoff bandwidth for TE polarization is 0.5 nm and the rejection ratio is 9 dB.
IR terahertz-bandwidth InGaAs MSM photodiode for communications and sensing applications
Author(s):
Jules D. Levine;
Michael O'Hagan;
James R. Palmer;
Gary E. Halama;
James A. McAdoo;
Dustin Carr;
Marc Currie;
Thomas Y. Hsiang;
Jianliang Li;
Louise Lorenzo;
Carlo Williams
Show Abstract
The insatiable desire for bandwidth has compelled many technological advances in communications system components over the last two decades. Fiber optics communications bandwidth has advanced at almost exponential rates with the developments of low-loss, singlemode fibers, EDFAs, and WDM technology which uses multiple lasers on a single fiber. The SilkRoad Corporation has taken a different approach to increasing available BW by using a single, but, very stable, laser and IR photodiode detectors of unparalleled BW.
Anomalous gain saturation in EDFAs
Author(s):
Diana Tentori-Santa-Cruz;
Manuel May;
Horacio Soto;
Javier Mendieta
Show Abstract
Several models have been developed to describe the interaction between neighboring ions in heavily doped erbium fibers. All of them are based on the anomalous saturation of the pump power. In this work we present experimental results of the anomalous behavior of the gain saturation in an EDFA, induced by the signal's power. This additional information shows us that energy migration is also induced by phonons.
Powers of transfer matrices and cyclic cascades
Author(s):
Tatiana Alieva;
Martin J. Bastiaans
Show Abstract
The parameters of the transfer matrix describing a first- order optical system that is a cascade of k identical subsystems defined by the transfer matrix M, are determined from considering the subsystem's eigenfunctions. A condition for the cascade to be cyclic is derived. Particular examples of cyclic first-order optical systems are presented.
Pseudo-symmetric beams: generation, propagation properties, and measurements
Author(s):
George Nemes;
Julio Serna;
Bernd Eppich;
Chunyu Gao;
Horst Weber
Show Abstract
We define the pseudo-symmetrical (PS), or the non-rotating general astigmatic beams, and investigate them theoretically and experimentally. We show that to any type of symmetrical beam, such as stigmatic, aligned simple astigmatic, or rotated simple astigmatic, corresponds a type of PS beam, which we call pseudo-stigmatic, pseudo-aligned simple astigmatic, and pseudo-rotated simple astigmatic, respectively. The PS beams behave identical to the symmetrical ones as long as only rotationally symmetric optical systems are involved, and as long as the second- order moments method is used to characterize these beams. We show how to characterize the PS beams using this method, how to generate them, we study their propagation properties, and show how to identify and measure them in comparison to the measurement of the symmetrical beams.
Propagation invariance and 3D light fields
Author(s):
Joseph Shamir;
Rafael Piestun;
Yoav Y. Schechner
Show Abstract
Wave-fields that propagate in free space while maintaining invariant characteristics are important for technological applications and they are interesting from a fundamental point of view. Conditions for generalized propagation- invariant wave-fields are discussed and specific examples are presented. Propagation invariance in a limited region of space is considered as well.
Degrees of freedom of an electromagnetic wave
Author(s):
Rafael Piestun;
David A. B. Miller
Show Abstract
We present a rigorous formalism for evaluating the degrees of freedom (d.o.f.) in communication with electromagnetic waves. We show that, although in principle there is an infinity of d.o.f., the effective number is finite. This is in agreement with the restricted classical theories. We further show that the best transmitting functions are the solutions of a specific eigenvalue equation. The analysis is valid for electromagnetic waves under arbitrary boundary conditions communicating between domains in 3D space. The practical implications of this theory will be discussed.
Zero twist of Gaussian light in first-order optical systems
Author(s):
Martin J. Bastiaans
Show Abstract
The propagation of Gaussian light through first-order optical systems is studied; in particular, the twist in the output (or input) plane is expressed in terms of the characteristics of the light in the other plane. Conditions are derived for which zero twist in the input plane corresponds to zero twist in the output plane, and vice versa. Three special cases for which zero twist is preserved, are described: (1) propagation between conjugated planes, (2) adaptation of the signal to the system, and (3) the case of symplectic Gaussian light.
Superresolution applied to solar granulation images
Author(s):
Noriaki Miura;
Naoshi Baba;
Takashi Sakurai
Show Abstract
Superresolution is attained for solar granulation images observed from the ground. The images are preprocessed with a blind deconvolution method, and then are superresolved. The resultant images show features with resolution higher than the diffraction limit.
MOMS/PRIRODA mission on the MIR station
Author(s):
Franz Lanzl
Show Abstract
MOMS is a live lens space camera for multispectral and stereo imaging. It was flown for the first time on a Space Shuttle mission (STS 55) in l993 in this 10-day mission approx. 7 million square km of the earth surface were covered. After the Shuttle flight the camera system was refurbished and adapted to the new environmental conditions onboard the PRIRODA-Module of the Russian MIR Space Station. Additionally, the MOMS-payload was extended by a navigation package consisting of a high precision gyro and a GPS system in order to provide the necessary position and attitude data for photogrammetric evaluation of the image data. MOMS-2P was launched into orbit in May 1996 and started its first operation in October 1996. Until end of 1998, approx. 50 million square km have been covered, mainly in the stereo mode. A tecimical description of the camera system and its operational concept will be presented as well as the present status of data recording. Information how MOMS data can be accessed and ordered will he given.
Light amplification by multilayers with fractal gain structures
Author(s):
Takashi Okamoto
Show Abstract
The transmission properties of an interference filter with optical gain are studied in which the layers of a gain medium are stacked in a self-similar manner. It is found that the gain variation of transmitted light with layer thickness or input frequency exhibits a fractal structure with sharp gain peaks which are not observed for a multilayer with periodic gain structures.
Complete system for characterization of spectrally selective fiber optic devices
Author(s):
Eli S. Simova;
Chander Prakash Grover
Show Abstract
We present an optical setup for complete characterization of fiber Bragg gratings and wavelength selective fiber-optic devices. We measure the spectral response of these devices either in transmission or in reflection geometry, and the wavelength dependency of the group delays due to chromatic and polarization mode dispersion, as well as the wavelength dependency of the polarization dependent loss.
Waveguide grating coupler with tailored wavelength response
Author(s):
Ming Li;
Yan Feng;
Baozhu S. Luo;
Hui Chun Liu;
Chander Prakash Grover
Show Abstract
We propose and experimentally demonstrate a novel method which, for the first time to our knowledge, makes it possible to tailor the wavelength response of a waveguide grating coupler. Such grating couplers may be used to improve the efficiency of broad-band quantum-well infrared photodetectors and solar cells.
Storage and retrieval of coherence functions using instantaneous holograms
Author(s):
Tomohiro Shirai;
Emil Wolf;
Girish S. Agarwal;
Leonard Mandel
Show Abstract
A novel method is described for storing and retrieving the second-order correlation function of partially coherent fields. The key element of the method is an instantaneous hologram that records the superposition of a random field whose correlation function is to be determined and the mutually incoherent reference field, taken over a time interval that is much shorter than the coherence time of the random field. The method is somewhat similar to conventional holography, but differs from it in several important respects.
Interferometric imaging by inverse propagation of cross-spectral density
Author(s):
Hidenobu Arimoto;
Kazuyoshi Itoh
Show Abstract
New imaging method based on measuring the spatial coherence function across an observation area is presented. The propagation law of the cross-spectral density described in the Fourier domain allows us to retrieve the cross-spectral density at arbitrary reference planes. The method can be applied to a source of any state of coherence. Results of the experimental demonstration are also shown.
Mutual influence of polarization and propagation of the light and symmetry of a space
Author(s):
Natalyia D. Kundikova
Show Abstract
The light polarization and its process of propagation are mutually independent under a narrow light beam propagation through a homogeneous medium. But it is not correct for the case of inhomogeneous medium. The influence of the trajectory on the light polarization consists in the rotation of the polarization plane under light propagation along the nonpianar trajectory [1, 2]. The influence of the polarization on the light trajectory manifests itself under the total internal reflection. A linearly polarized reflected ray suffers a longitudinal shift [3, 4], and a circular polarized ray suffers transverse shift [5, 6]. It should be stressed that those investigations were independent and the effects were not considered as a result of manifestation of mutual influence of the polarization of the light and its propagation. For the first time professor B.Ya.Zel'dovich, dealing with the light propagation through a multimode optical fiber, has pointed out that the influence of the trajectory on light polarization and the influence of polarization on the light trajectory are mutually inverse effects [7]. On that base optical Magnus effect was predicted [711 and experimentally observed [8]. Optical Magnus effect manifests itself as a rotation of the speckle pattern of the circular polarized light transmitted through a multimode optical fiber under circular polarization sign change. In terms of quantum mechanics that effect was regarded as an interaction between orbital momentum of photon and its spin (polarization) [7]. All mentioned above effects exist in optically inhomogeneous medium. We can supposed that spin-orbit interaction of a photon manifests itself due to break down of the symmetry of a space, namely, the translation symmetry. Nevertheless, it was shown and experimentally observed that there exist influence of the polarization on the light trajectory under the light propagation through an optically homogeneous medium [9, 10]. That effect manifests itself under circular polarized light propagation through a half of lens: the focal spot of a beam suffers a transverse shift under circular polarization sign change. In that particular case the manifestation of spin-orbit interaction of a photon can be considered as a result of break down of the axial symmetry of a medium. That interpretation allows us to predict the existence of the inverse effect — the influence of the polarization on the light propagation in a homogeneous medium. Let us consider the propagation of the linear polarized light through a half of lens. The linear polarized light can be considered as a superposition of the left and right circular polarized light. According to [9, 10] the centers of gravity of the left and right circular polarized light will not coincide. Let us screen the half of the focal plane. The estimation based on the results [9] has shown that the transmitted light will be right or left elliptically polarized with degree of the ellipticity < iO. That scheme was experimentally realized. The change of the ellipticity of the correct sign was observed. The preliminary results were reported in [11]. That effect can be also considered as the geometric light depolarization.
Near-field effects in spatial coherence of thermal sources of light: short-range and long-range correlations
Author(s):
Jean-Jacques Greffet;
Remi Carminati
Show Abstract
In this paper, we establish the form of the spectral degree of spatial coherence of the field thermally emitted by a planar opaque surface. Our approach is based on the fluctuation-dissipation theorem. Several new properties are derived. It is shown that for lossy media, the coherence length in a plane very close to the surface is essentially the skin depth. Thus, it can be much smaller than the wavelength. However, if the metal can support a surface wave, the coherence length can be much larger than the wavelength.
Efficiency of organic light-emitting diodes
Author(s):
Alexander L. Burin;
Mark A. Ratner
Show Abstract
We have studied the quantum efficiency of multilayer organic light emitting diodes (OLEDs). Attention is focused on the recombination efficiency and exciton quenching, controlling the performance of highly efficient OLEDs having Alq(3) (Al(III) 8-hydroxyquinoline) as the emissive layer. The kinetics model is extended to account for the image charge effect on the injection and the narrow bandwidths of carriers. An analytical criterion for maximum recombination efficiency at low voltages is found. The analysis of current voltage dependence and quantum efficiency is performed for Al/LiF/Alq(3)/TPD/ITO devices with or without an ultrathin dielectric layer LiF, taking into account the exciton quenching controlled by the boundary Al-Alq(3). We get a reasonable fit for the experimental data and discuss the optimum modifications required to enhance the device performance.
Pulsed photothermal measurement of tetrahedral amorphous carbon (ta-C) film
Author(s):
George C. K. Chen;
Ping Hui
Show Abstract
Pulsed photothermal reflection technique is developed to measure the thermal conductivity of tetrahedral amorphous carbon (ta-C) films. This technique is basically a pump and probe type. The pump source is Nd YAG laser, pulse width 8 ns, is operated at 532 nm with 1 mJ. The sample is deposited on silicon wafer and over-coated with a gold layer for heat absorption. Upon the laser pulse strikes on the sample surface, the surface temperature rises sharply and then relaxes with time. A continuous HeNe laser (1 mW) probes the surface temperature, measuring the reflectivity changes on the sample's surface. Since the reflectivity and temperature has an inverse linear relationship, the relaxed temperature profile can be obtained by inverting the captured reflectivity profile. Using either 2-layer or 3-layer heat conduction model, thermal properties of the ta-C film are then varied to fit the obtained profile. The fitted thermal conductivity value of the ta-C film is approximately 2 W/mK.
Raman study of deformation of polyethylene
Author(s):
Kirill A. Prokhorov;
G. Yu Nikolaeva;
Pavel P. Pashinin;
Sergey A. Gordeyev;
Ludmila E. Semenova
Show Abstract
Oriented polycrystalline polymers with high mechanical properties are very important for many practical applications. Such materials can be produced by drawing at temperatures near to their melting point. During the drawing process, macromolecules are aligned along the drawing direction, which leads to a considerable increase in the Young's modulus, strength and stiffness of polymer. The orientation distribution function of macromolecules is one of the most significant characteristics of the structure of oriented polycrystalline polymers. The coefficients of the distribution function expansion in a series of generalised spherical harmonics can be determined by several techniques, such as X-ray analysis, IR-spectroscopy, and birefringence measurements. Raman spectroscopy is one of the most convenient and informative tools for studying the orientation of macromolecules. It has been shown that Raman spectroscopy is capable of determining the expansion coefficients up to the fourth order for both crystalline and amorphous phases [1,2]. At present, Raman spectroscopy is often used to study the orientational order in a various polycrystalline polymers (see references from [3]). Here we present the investigation of mechanism of uniaxial deformation of polyethylene from the isotropic state to the extremely drawn state (when increasing the draw ratio causes the sample to break apart).
Some peculiarities of rotation of polarization plane in quartz
Author(s):
Ivetta T. Bodnar
Show Abstract
In the present work some results of modulation peculiarities measurements of linearly polarized laser beam are obtained. The laser beam with polarization under 45 degree(s) angle to the optical axis of quartz passed through quartz crystal set between two crossed polarizers. The intensity of laser beam after passing through the polarizer-crystal-analyzer system was measured in dependence of the turn angle of crystal. It is determined that every pair of parallel faces of quartz cube has its individual modulation intensity picture. Experimentally conditions do not influence the whole picture. It is supposed that different kinds of modulation can be connected with certain crystallographic directions.
Optical characterization of multilayer systems with randomly rough boundaries
Author(s):
Ivan Ohlidal;
Frantisek Vizd'a;
Miloslav Ohlidal
Show Abstract
In this contribution examples of the optical characterization of multilayer systems with randomly rough boundaries are presented. The method based on measuring and interpreting the spectral dependences of the coherent reflectance is used to determine the values of the optical and statistical parameters of samples of three-layer and thirteen-layer systems exhibiting the rough boundaries. The systems mentioned are formed by thin films of SiO2 and TiO2.
WDM soliton transmission in dispersion-managed links
Author(s):
Thierry Georges;
Francois Favre
Show Abstract
Dispersion-managed solitons exhibit superior transmission quality as soon as Kerr nonlinearity in non negligible. Long transmission distances, large span loss and high spectral efficiency are expected for the next generation of transmission systems based on 20 Gbit/s and 40 Gbit/s data rate.
Experimental results on high-bit-rate optical synchronization of RZ soliton-type signals
Author(s):
Pedro Miguel Tavares;
Orlando Frazao;
Antonio Cunha;
L. Botelho Ribeiro;
Jose Ferreira da Rocha
Show Abstract
We report the development of a lab prototype for all optical synchronization at 10 GHz. Adjusting the distance between the AR coated facet of the MQW semiconductor laser and the ferrule it was possible to induce the self-pulsation needed for correct operation. In the presence of optical RZ signals, the device leaves is natural pulsation frequency synchronizing with the input data.
Design aspects of soliton communication systems
Author(s):
Mario F. S. Ferreira
Show Abstract
We examine the main constraints on the design of single- channel, high-bit rate soliton communication systems. In the average soliton regime, the main limitation for transoceanic fiber links is the Gordon-Haus jitter, while for shorter transmission distances it arises from the discrete in-line amplification. The use of dispersion-decreasing fibers and of periodic optical phase conjugation can increase the system capacity.
Optical networking advances in Europe
Author(s):
Paul E. Lagasse;
Piet M. A. Demeester;
Ann Ackaert
Show Abstract
After a short introduction on the European Union RTD Programs, a more in-depth analysis will be given on the projects and results recently obtained within in the ACTS (Advanced Communications and Services Program) Photonic Technologies Area.
Imaging methods that ensure positive images
Author(s):
Eric Clarkson;
John L. Denny
Show Abstract
We discuss methods of image reconstruction which lead to non-negative images: no negative values appear in the estimate or approximation to the unknown object. We describe methods which always lead to non-negative estimates of the object, characterize some regularized and non-regularized methods, and characterize those orthonormal systems whose partial series approximations to the object are always non- negative. This paper surveys the authors' recent research, adds some new results, and discusses related work.
Phase retrieval algorithms in the Fresnel domain
Author(s):
Ido Raveh;
Emanuel Marom;
David Mendlovic
Show Abstract
There are several known iterative algorithms, which reconstruct the phase of an unknown wavefront from two intensity measurements. These algorithms are based on a Fourier connection between the input and output plane. An algorithm based on a Fourier connection must contain additional optical setup for the implementation and in addition needs more longitudinal space. Since a wavefront is a function that obeys the wave equation, it is only natural to implement the iterative algorithms using free space propagation relation between two intensity planes. We propose to make phase retrieval calculations between any two arbitrary planes interrelated through the Fresnel domain. Since any two arbitrary parallel planes are interconnected by the Fresnel domain, no additional setup is needed. The calculation of the free space propagation is based on the angular spectrum approach, which is calculated using the fast Fourier transform. This approach can be applied with any of the algorithms that rely on a Fourier connection between the input and the output planes.
Blind image deconvolution for symmetric blurs by polynomial factorization
Author(s):
Edmund Yin-mun Lam;
Joseph W. Goodman
Show Abstract
In image acquisition, the captured image is often the result of the object being convolved with a blur. Deconvolution is necessary to undo the effects of the blur. However, in reality we often know very little of its exact structure, and therefore we have to perform blind deconvolution. Most existing methods are computationally intensive, Here, we show that if the blur is symmetric, we have an efficient algorithm for deconvolution based on polynomial factorization in the z-domain.
Monitoring the reduction of multiplicative noise in periodic patterns
Author(s):
Adolf W. Lohmann;
Claudio Frausto;
Jorge Ojeda-Castaneda
Show Abstract
We exploit the random superposition process for presenting a statistical model that describes the reduction of multiplicative noise, on a periodic structure, by using the self-image phenomenon. We discuss a novel, noncoherent, optical processor for visualizing this reduction process, in a single picture. Numerical simulations are reported.
Heterodyne temporal speckle pattern interferometry
Author(s):
Hans J. Tiziani;
Mahendra P. Kothiyal;
Charles Joenathan;
Pascal Haible
Show Abstract
Multiple wavelength interferometry is used to increase the range of unambiguity beyond that of single wavelength interferometry. In wavelength scanning interferometry, the frequency of the intensity modulation induced by the wavelength change is determined independently for each image pixel. The tuning range determines the resolution of measurements, while the tuning step limits the range of the measurements. Laser diodes can be tuned, but an external cavity is needed for a larger mode hop free wavelength variation. Polished and optically rough surfaces can be analyzed in the same manner. Acquisition times of a few seconds and high resolutions were obtained. In a new development, the application of temporal evaluation of speckles for deformation and shape measurement will be discussed. It turns out that spectral and temporal phase analysis can be very useful for many applications in optical metrology.
Measurement considerations for precise highly reflective surfaces using a phase-measuring Fizeau interferometer
Author(s):
Katherine Creath
Show Abstract
Stringent surface specifications for highly reflective precision optical surfaces place great demands on interferometric techniques used for surface metrology. Highly reflective test surfaces often produce nonsinusoidal interference fringes when compared to a partially- reflective/absorbing reference surface in Fizeau-type interferometers. This talk will discuss some tradeoffs in choosing phase-measurement techniques for use with noticeably nonsinusoidal fringes when the residual measurement error needs to be on the order of one-hundredth of a wave peak-to-valley. The errors due to the phase calculation algorithm, the phase shift calibration and the reference surface calibration are all coupled making the choices more difficult. Simulated data will be used for most of the discussion. Comparisons to the measurement of uncoated surfaces will be made.
Precision optics for long baseline interferometry
Author(s):
Achim J. Leistner;
Bozenko F. Oreb;
Christopher J. Walsh
Show Abstract
Optical interferometers are being built to operate over longer and longer baselines, in some cases more than a few kilometers. Examples include laser interferometers to detect gravitational waves, and stellar interferometers which use starlight to determine the angular diameter of the source. The optics used in these interferometers must satisfy demanding performance criteria. In this paper we review some of those criteria and present results which demonstrate that such optical surfaces can be successfully fabricated and measured.
Fourier synthesis of 257-GHz optical pulse trains using three cw semiconductor lasers
Author(s):
Masaharu Hyodo;
Noriaki Onodera;
Kazi Monowar Abedin
Show Abstract
Fourier synthesis of 257-GHz optical pulse trains has been demonstrated based on optical phase locking of three independent continuous-wave semiconductor lasers using SOA as a four-wave mixer. The FM sideband heterodyne technique was employed to ensure the stable homodyne optical phase locking. The SHG correlation traces were measured for several phase-locking offsets, and were in good agreement with theory.
Time-delayed nonlinear absorption effects on spatiotemporal propagation for femtosecond pulses
Author(s):
Mary J. Potasek;
Sukkeun Kim
Show Abstract
We investigate the effects of time delayed nonlinear absorption (Raman effect) on spatiotemporal propagation for femtosecond pulses. In the case of normal dispersion and no Raman effect, we find symmetric pulse splitting, in agreement with previous work. However, as the magnitude of the Raman effect increases relative to the dispersion, asymmetric splitting occurs. For significant Raman effect, the pulse splitting due to GVD is suppressed.
Application of volume-phase self-developing Fourier holograms in Vander Lugt optical processor
Author(s):
Eugene A. Tikhonov;
Mykhajlo V. Shovgenyuk
Show Abstract
The optical correlator is considered as an effective type of coherent optical processor with parallel way of data processing. Two basic schemes of the optical correlator are known: one with frequency plane (or Vander Lugt correlator) and second one with the joint Fourier transformation. The authors of the given work are concerned with a problem of the pattern coding and recognition for a number of the static images.
Color optical pattern recognition using nonlinear morphological correlation
Author(s):
Pascuala Garcia-Martinez;
Carlos Ferreira;
Javier Garcia;
E. Signes
Show Abstract
The morphological correlation has been recently used as a tool in optical pattern recognition owing to its nonlinear properties. In this paper, we present an extension of the morphological correlation to color pattern recognition. We use two methods: the multichannel one, based on decomposing the image in separate channels, and the single channel method, based on codifying the color information into a single amplitude/phase distribution. Simulation results are given and optical implementation is proposed.
Multiple target detection using a wavelet joint transform processor
Author(s):
Mohammad S. Alam;
Dylan Chain
Show Abstract
An improved multiple target detection technique is proposed by using a wavelet joint transform correlator (JTC). A bank of wavelet filters are generated using the Mexican hat wavelet function which are sequentially superimposed on the joint power spectrum before applying the inverse Fourier transform to yield the correlation output. This technique is found to yield high correlation discrimination for multiple target detection for both binary and grey level input scenes while avoiding the false alarms as well as rejecting the non-target objects. An all-optical implementation for the proposed wavelet JTC technique is also suggested. Computer simulation results are presented to confirm the effectiveness of the proposed technique.
Optical classification employing composed gray-level CGH filters
Author(s):
Claudio C. Iemmi;
Silvia A. Ledesma;
Juan Campos;
Mirta Villarreal
Show Abstract
Synthesis of gray level computer generated holograms allows to increase the information storage capability of complex filters. In this work we study the capability of gray level filters to perform multichannel correlation. To this end a composed synthetic discriminant function filter is employed to implement an object classification by means of a binary code.
Wavelet transform to improve recognition accuracy of a volume holographic correlator
Author(s):
Wenyi Feng;
Yingbai Yan;
Guofan Jin;
Minxian Wu;
Qingsheng He
Show Abstract
Volume holographic associative storage in a photorefractive crystal provides an inherent mechanism to develop a multichannel correlation system with high parallelism. Wavelet transform is introduced to improve recognition accuracy of the system. A novel volume holographic correlator is proposed and constructed. Its application in human face recognition is studied, and experimental results are given.
White light JTC for color pattern recognition
Author(s):
Hongchen Zhai;
Xiushan Zhu;
Guoguang Mu
Show Abstract
We present theoretical analysis and experimental results of a white light JTC (joint transform correlator) using a tri- color grating to encode color patterns. The power spectra of the encoded pattern are easy for parallel channeling, and the zero order power spectrum also forms an important channel for the shape-only correlation.
How knowledge about speckle intensity and phase gradients can improve electronic speckle pattern interferometry
Author(s):
Heinz Helmers;
Jan Burke
Show Abstract
As is well known, the spatial coherence in a speckle field is limited to an area called the mean speckle size. Throughout this area, the coherence decays smoothly from the center to the margin of a speckle, and the degree of coherence between two points (x1,y1) and (x2,y2) determines the probable amount of deviations between their intensities I1, I2 and phases. These deviations are of special importance when spatial phase shifting is applied in electronic speckle pattern interferometry. We demonstrate that the knowledge about the intensity and phase gradients in the object speckle pattern can be used to reduce the noise in measured deformation maps significantly.
Real-time and unambiguous visualization of a surface profile using an all-optical feedback interferometer
Author(s):
Tomohiro Shirai;
Thomas H. Barnes;
T. G. Haskel
Show Abstract
A novel feedback interferometer, which consists of a polarization Sagnac interferometer and an optically- addressed phase-only spatial light modulator, is described for real-time and unambiguous visualization of the surface profile. In this system, the output intensity from the Sagnac interferometer is optically fed back to the phase modulator placed in one arm of the interferometer to produce a sawtooth fringe intensity profile which is directly and unambiguously related to the surface profile. Experimental results demonstrate the feasibility of applying this system to surface profile measurement.
Adaptive optical 3D measurement with structured light
Author(s):
Joerg Gerber;
Richard M. Kowarschik;
Gunther Notni;
Wolfgang Schreiber
Show Abstract
The basis of the described 3D-measurement system is the method of fringe projection in combination with the principle of uniform scale representation /1 1, /2/, /3/. The measurement is characterized by the exclusive use of phase-measurement values for the coordinates of each point. To obtain the phase-measurement values the object under test is successively illuminated with a grating structure from at least three different directions with a telecentric system. A CCD-camera records the intensity distribution of the fringes intersected by the object. It should be pointed out that the values of all coordinates (x,y,z) have the same accuracies. The object to be measured and the CCD-camera are both mounted on a rotation table, turning both of them with respect to the fringe-projector about an axis. The rotation axis makes a constant angle c with the projection direction. With at least i = 3 different angle values e the linearly independent absolute phase values are obtained, which are necessary for the coordinate calculation (applying gray-code in conjunction with four 90 degs phase-shifts). In our setup we can choose up to I = 1 5 rotation angles, so that awkward areas of the surface, like zones with either specular reflection or shadows, are shifted over the surface and have nearly no influence on the results of measurements. So, we obtain the 3D-coordinates of a single patch of the object. We have expanded the system to include a second rotation axis, where the object can rotate within the measurement volume. The CCD-camera will then get different views of the object. The second rotation axis is tilted against the first axis by an angle S. Depending on the class of objects there are different possible tilt-angles S. Typically we choose ö = 300. By rotating the object around the first axis with a rotation angle -y (j = number of patches) it is possible to measure the object from different viewpoints, whereby for each patch or viewpoint the procedure described above is used. For a convenient handling of the data-set the restriction j 8 is used. The actual rotation angles e and y were measured with angle encoders. The free geometric parameters (grating periode A and projection angle a) and the orientation in space of the second axis are gauged before the measurement procedure as described below. By measuring a number of patches we have the problem of transforming them from a local coordinate system into a global one. The combination of the different patches into one coordinate system without interactive user help was solved by developing a calibration method for the second axis. In combination with an absolute phase measurement all patches were measured in a known space orientation, so that we obtain the 3D-picture by rotation of each patch around the second axis. Correlation methods or special points are not necessary. To obtain the 3Dorientation of the second axis one can use a calibration procedure with a special calibration body whose 3Dcoordinates are measured for different rotation positions whereby the second axis has to cross the plane near the centre.
Remarkable lenses and eye units in statues from the Egyptian Old Kingdom (ca. 4500 years ago): properties, timeline, questions requiring resolution
Author(s):
Jay M. Enoch
Show Abstract
The first known lenses appeared during the IVth and Vth Dynasties (fabricated mainly between ca. 2500 - 2400 BC) of the Old Kingdom of Egypt. Excellent examples of these lenses are found in The Louvre Museum in Paris and the Egyptian Museum in Cairo. These lenses were components of eye constructs in statues and had unique qualities. In particular, the `eyes' appear to follow the viewer as he/she rotates about the statues in any direction. Clearly, this was an intended effect which can be readily photographed (and understood optically). The lenses were ground from high quality rock crystal (a form of quartz). They had a convex and highly polished front surface. On the plane rear lens surface as `iris' was painted. Centered in the dark- appearing pupil zone was an approximately hemispheric negative ground, high power, concave lens surface.
Analysis of an optical attractive force exerted upon metallic particles
Author(s):
Hiromitsu Furukawa
Show Abstract
Optical tweezer is a powerful tool for manipulating samples under a microscope. However, this technique is limited to transparent objects because it has been believed that it is the light refraction that play a significant role to manipulate the microscopic objects. We took notice of a optical force generated by a surface diffraction wave, so called creeping wave [1] , and found that it can be applicable to trap metallic objects [21. In this presentation, we show that gold Mie particles (0.5 - 3.0 im in diameter) can be trapped optically in two dimensions.
Future of femtosecond technology
Author(s):
Ursula Keller
Show Abstract
Today, ultrafast laser technology demonstrates unsurpassed performances in terms of pulse duration, pulse repetition rates, average power and wavelength range. This enables new applications in many areas such as optical communication, photonics switching, RGB-displays, material processing and many more. These markets will strongly drive further research efforts towards even more reliable and more compact sources. In addition, we are at the edge of sub-femtosecond science using high-harmonic generation of optical pulses with only few optical cycles.
Suboptical wavelength atomic gratings generated in a time-domain interferometer
Author(s):
Andrey V. Turlapov;
Dmitry V. Strekalov;
A. Kumarakrishnan;
Sydney B. Cahn;
A. Karpf;
Tycho Sleator
Show Abstract
We have studied sub-optical wavelength atomic gratings generated by the interference of atomic de Broglie waves in a time-domain interferometer. Three short optical standing- wave pulses, detuned from resonance with a cloud of approximately 100 (mu) K 85Rb atoms, act as phase gratings for atomic matter waves. Shortly after the first pulse, a modulation in the atomic density containing spatial harmonics of period (lambda) /2N appears ((lambda) is the optical wavelength, and N is any integer) and then rapidly vanishes due to the atomic thermal motion. The cloud maintains phase memory of this modulation, however, and the second pulse (applied at time T after the first one) results in a temporal sequence of atomic density gratings of periods (lambda) /2N. The appearance of a grating is referred to as an echo. The third pulse (and a subsequent traveling wave pulse) is used to detect these gratings. By this technique, we have created and detected in real time a grating with period (lambda) /4 at time 1.5T after the first pulse and observed new types of `echoes' caused by interaction of the de Broglie waves with all three phase gratings. This ability to produce sub-wavelength structures makes our techniques applicable to atomic beam lithography.
Imaging of phase-space evolution of trapped atoms
Author(s):
Dmitry V. Strekalov;
Andrey V. Turlapov;
A. Kumarakrishnan;
A. Karpf;
Tycho Sleator
Show Abstract
Experimental results on phase-space imaging of a laser- cooled atomic cloud are presented. Both position and velocity information are encoded in the frequency of the signal coherently radiated from the cloud. This encoding is achieved by application of a position-dependent magnetic field. Fourier transformation of the signal yields a projection of the phase-space density of the atoms. Imprinting a structure on the cloud we observe its time `sheering' evolution in the phase-space. Since the projection direction is determined by the imposed field gradient, we can reconstruct the phase-space structure of the cloud.
Modulator and VCSEL-MSM smart pixels for parallel pipeline networking and signal processing
Author(s):
C.-H. Chen;
Bogdan Hoanca;
C. B. Kuznia;
Dhawat E. Pansatiankul;
Liping Zhang;
Alexander A. Sawchuk
Show Abstract
TRANslucent Smart Pixel Array (TRANSPAR) systems perform high performance parallel pipeline networking and signal processing based on optical propagation of 3D data packets. The TRANSPAR smart pixel devices use either self-electro- optic effect GaAs multiple quantum well modulators or CMOS- VCSEL-MSM (CMOS-Vertical Cavity Surface Emitting Laser- Metal-Semiconductor-Metal) technology. The data packets transfer among high throughput photonic network nodes using multiple access/collision detection or token-ring protocols.
VLSI smart pixel array for free-space optical interconnects
Author(s):
Christine T. Mollenkopf;
Jongwoo Kim;
John M. Hessenbruch;
Jack Ko;
Richard V. Stone;
Peter S. Guilfoyle
Show Abstract
VLSI smart pixel arrays are being developed for free space optical interconnects in high density input/output applications. An individual smart pixel cell, which operates at 850 nm, consists of a vertical cavity surface emitting laser, a photodetector, an optical receiver, a laser driver, and digital logic circuitry. For optical interconnect applications, the integrated smart pixel combines high speed operation and low power consumption. A 32 X 32 smart pixel array is currently being developed that will operate at 500 Mbps/channel, which gives an aggregate throughput of > 500 Gbps with a power consumption of < 10 W.
Controlling distortion in an optical imaging system
Author(s):
Dayong Wang;
Avi Pe'er;
Asher A. Friesem;
Adolf W. Lohmann
Show Abstract
We present a system in which it is possible to distort the intensity distribution of an object I(x,y) into I(Ax + By,Cx + Dy), where the ABCD matrix has a unit determinant. The coefficients A, B, C and D can be varied independent of each other by rotating some cylindrical lenses. The degree of coherence is arbitrary. The number of pixels is limited in the usual way by the size of the object, by the wavelength, and by the F-number of the lenses.
Fusion study on optical correlation pattern recognition and neural networks
Author(s):
YanXin Zhang
Show Abstract
From the view point of neural networks (NNs) the present problems of optical correlation pattern recognition (OCPR) are analyzed. It is shown that distortion invariant pattern recognition (DIPR) can not be performed with a single filter within the framework of OCPR. By means of fusion between OCPR and NNs some solutions to an effective optical DIPR are proposed.
Optics for the National Ignition Facility
Author(s):
L. Jeffrey Atherton
Show Abstract
The National Ignition Facility (NIF) is a 192 beam, 1.8 megajoule laser currently under construction at LLNL. The laser requires approximately 7,500 meter class optical components including 3,000 phosphate laser glass slabs, 2,500 fused silica lenses and windows, 1,400 BK-7 mirror and polarizer substrates with hafnia/silica multilayer coatings, and 600 KDP and deuterated KDP (DKDP) nonlinear crystals, each component with a 40 cm square aperture. These optics will be produced between 2000 and 2003 following pilot production campaigns to prove the technologies in 1999. The specifications of these large optics are challenging, with a typical wavefront gradient of Xi90/cm RMS,and damage thresholds of 14 J/cm2 (351 nm) and 20 J/cm2 (1053 nm) for 3 ns pulses. The cost goals for producing each of these optics vary, but on average are approximately three-times lower than we paid for Beamlet and Nova optics.
Wavefront control system for the National Ignition Facility (NIF)
Author(s):
Richard A. Zacharias;
Erlan S. Bliss;
Mark Feldman;
Andrew Grey;
Jeffrey A. Koch;
Richard A. Sacks;
John S. Toeppen;
Lewis Van Atta;
Scott Winters;
Bruce W. Woods
Show Abstract
The use of lasers as the driver for inertial confinement fusion experiments and weapons physics applications is based on their ability to produce high-energy short pulses in a beam with low divergence. Indeed, the focusability of high quality laser beams far exceeds alternate technologies and is a major factor in the rationale for building lasers for such applications The National Ignition Facility (NIF) is a large 192-beam laser facility now under construction at the Lawrence Livermore National Laboratory for fusion and weapons physics experiments. Its uncorrected focal spot minimum size is limited by wavefront aberrations in the laser system. NIF is designed with a wavefront control system to correct these aberrations to yield a focal spot that is small enough for NIF' s intended applications. Sources of aberrations to be corrected include prompt pump-induced distortions in the laser amplifiers, thermal distortions in the amplifiers from previous shots, beam off-axis effects, and gravity, mounting, and coating-induced optic distortions. Aberrations from gas density variations and manufacturing figure errors in the optics are also partially corrected by the wavefront control system. The NIF wavefront control system consists of five subsystems for each of the 192 beams: 1) a deformable mirror, 2) a wavefront sensor, 3) a computer controller, 4) a wavefront reference system, and 5) a rapid reconfiguration system to allow the wavefront control system to operate to within one second of the laser shot. The system includes the capability for in situ calibrations and operates in closed loop prior to the shot. Shot wavefront data is recorded. This paper describes the function, realization, and performance of each wavefront control subsystem. Subsystem performance will be characterized by computer models and by test results. The focal spot improvement in the NIF laser system effected by the wavefront control system will be characterized through computer models. The sensitivity of the target focal spot to various aberration sources will be presented. Analyses to optimize the wavefront control system will also be presented.
Aspherical surface testing by using spherical compensation
Author(s):
Johannes Pfund;
Norbert Lindlein;
Johannes Schwider
Show Abstract
A technique for testing aspherical surfaces without the use of a null-corrector is described. The wave-front sensor for the detection of the aspherical wave-front is a Shack- Hartmann sensor which has a significantly expanded range of measurable wave-front slopes. The optical testing set-up, the used algorithm for the dynamic range expansion, and experimental results are presented in this paper.
Matrix method for the analysis of optical waveguides and quantum well structures
Author(s):
Ajoy K. Ghatak
Show Abstract
The design of devices, components or systems using optical fibers and integrated optical waveguides, involves the solution of the wave equation under specific boundary conditions. Although in some situations one can obtain analytical solution to the problem, in most cases the problem needs to be tackled numerically. For example, in devices using graded index waveguides or bent waveguides, in general one cannot obtain analytical solutions. In order to tackle such problems many numerical techniques have been developed in the literature. The matrix method which forms the subject matter of this talk is one such method developed by us. This method has been used for obtaining the propagation characteristics of planar graded index waveguides, bent planar waveguides, cylindrical optical fibers with an arbitrary refractive index profile and quantum well structures. One of the most important attributes of this method is the fact that this method can yield complex propagation constants of an optical waveguide without performing any complex plane iterations and hence can be used as a method to predict starting values in any complex plane iteration program. Using this technique one can also obtain the leakage losses in waveguides and in particular in depressed cladding fibers.
New generation of very high repetition rate subnanosecond pulsed UV sources
Author(s):
F. Druon;
Francois Balembois;
Patrick M. Georges;
Alain Brun
Show Abstract
We demonstrate a new kind of picosecond laser source in the UV at high repetition rate. This system is based on only passive, compact and simple elements: a microchip laser and a very efficient multipass amplifier both pumped with recently developed high brightness laser diodes. This all- solid-state laser has been optimized for delivering, at a high repetition rate -45 kHz-, sub-nanosecond pulses at the wavelength of 355 nm with an energy per pulse close to 1 (mu) J (or equivalently 38 mW average power). This source is- -to our knowledge--the first totally passive, 300-ps UV laser source at this high repetition rate.
Linear and nonlinear propagation of femtosecond laser pulses in dispersive media
Author(s):
Czeslaw Radzewicz
Show Abstract
Some aspects of the propagation of femtosecond laser pulses in transparent, dispersive, nonlinear media are reviewed. Since the details of pulse propagation depend critically on the experimental conditions we only will briefly consider a general case of a femtosecond wavepacket evolution and then apply it to specific problems. Theoretical and experimental results for wavepacket distortion by lenses and wavepacket distortion in birefringent media will be presented. Splitting of femtosecond wavepackets in dispersive Kerr media will be also discussed.
Upconversion lasing of a Tm3+-doped fluoride glass microsphere
Author(s):
Keiji Sasaki;
Hideki Fujiwara
Show Abstract
Upconversion lasing of a thulium-ion-doped zirconium fluoride glass microsphere was demonstrated. The microsphere was pumped by a fundamental wave of a Nd:YAG laser (1064 nm) at room temperature. The lasing emission was observed in 480-nm and 800-nm regions, and their lasing thresholds were determined to be approximately 20 mW and approximately 5 mW, respectively. The application to near-field optical microscopy is also discussed.
Submillisecond pulses by two-wave coupling in Bi12TiO20 crystals
Author(s):
Matthias Esselbach;
Gregor Cedilnik;
Armin Kiessling;
Richard M. Kowarschik
Show Abstract
We experimentally observed the unusually fast response in a two-wave mixing arrangement with fiber-like Bi12TiO20 crystals on transient change of the external electric field. Pulses of the amplification of the signal wave with a rise time down to 0.2 ms and a width of 0.5 ms at a total input intensity of 6 mW/mm2 are obtained when applying a rising or decreasing front of an external electric field to the crystal. The two-wave coupling without external field has a response time of 200 ms.
Photonics in digital computing: paradigms and proof-of-principle demonstrators
Author(s):
Hugo Thienpont
Show Abstract
It is generally recognized by the optics in computing community that photonic technologies can help to alleviate the data communication bottlenecks of future digital processing systems in two ways. In a first approach optics could be used as a wirereplacing technology at the different interconnect levels in computers such as the back-plane, the board-to-board, the multi-chip to multi-chip (MCM) and even the intra-MCM interconnect level. In a second approach 2D-arrays of smart pixels, which are integrated VLSI-photonic components that combine the electronic processing power of Si-CMOS with the high interconnect density of GaAs-based parallel opto-electronic I/O planes, could play a major role in dedicated processing systems such as smart focal-plane arrays, artificial retina and early-vision processors and outperform their dedicated all-electronic counterparts. In this paper we bring forward some of the multifarious ways to put micro-optical components to work in digital optical information processing systems by reviewing two of our most recent proof-of-principle demonstrators. First we will illustrate the "microoptics as a wire-replacing technology" paradigm by presenting a micro-optical module for multi-channel free-space intra-MCM interconnects. Secondly, as an example of the so-called "smart pixel" paradigm, we demonstrate how we have constructed a prototype morphological image processor based on 8x8 arrays of opto-electronic transceiver arrays
Experiments with new phase image encrypting method
Author(s):
Paul C. Mogensen;
Jesper Glueckstad;
Haruyoshi Toyoda;
Tsutomu Hara
Show Abstract
Recently, there has been considerable interest in the application of combined phase/amplitude encryption to the field of optical pattern recognition based security systems, due to the high level of security that it offers1. We have developed a new phase-only encryption technique based in principle on a phase-coding method which uses a generalization of the Zernike phase contrast technique, but breaks the small-phase-angle limitation of Zernike's method2. This phase-coding technique for image formation, in which the spatial average value of an input phase modulated image is combined with a pre-estimated phase retardation produced by a phase contrast filter, has been demonstrated experimentally3. In this paper we describe an extension of our phase-coding method4 and its application in an experimental system for the decryption and visualization of phase encrypted images using commercially available Parallel-Aligned Liquid Crystal Spatial Light Modulators (PAL-SLM) supplied by Hamamatsu Photonics5.
Encryption of optical image using BCGH and visual cryptography
Author(s):
Sang-Yi Yi;
Chung-Sang Ryu;
Dal-Gyu Kim;
Seung-Hyun Lee
Show Abstract
The thresholding scheme in which a person can decode the encrypted data with an important information in the agreement of other members has been extended to the visual data by visual cryptography. But with the limitation of visual cryptography in the representation of information, some problem is encountered in application. This paper proposes a method to overcome the problem by introducing an optical technique to the visual cryptography.
Interference anticounterfeiting using computer-generated hologram
Author(s):
Qizhong Huang;
Jinglei Du;
Yixiao Zhang;
Yongkang Guo
Show Abstract
An anti-counterfeiting method using CGH phase coding is presented in this paper. The phase of a wave-front is coded by means of detour phase coding and then interfere with a reference wave, which is also generated by CGH. The object recorded in the hologram can be read out from the interference patterns. The object can be easily generated by computer, caught by CCD camera or scanner, both black-white and grayscale object can be used in our method. The features of this method lies in that it is flexible in designing, easy to observation and reconstructed by common expanding white light source. The reference wave can be a plane wave or another phase coding wave, then it's difficult to duplicate an identical CGH based on the decoding information, this made it enjoy a high anti-counterfeiting ability.
Efficient optical negabinary signed-digit arithmetic operations and implementation using electron-trapping device
Author(s):
Guoqiang Li;
Feng Qian;
Hao Ruan;
Liren Liu
Show Abstract
A two-step carry-free negabinary signed-digit (NSD) addition/subtraction algorithm and the fast conversion algorithm from NSD to negabinary in the carry-look-ahead mode have been investigated. All the arithmetic operations can be performed with binary logic. By programming the binary reference bits, addition and subtraction can be realized in parallel with the same binary logic functions. Correspondingly, a compact general-purpose optoelectronic arithmetic-logic array system using electron trapping device is suggested. Various complex logic functions can be performed by programming the illumination of the data arrays without additional temporal latency of the intermediate results. Experimental results will be presented.
General paraxial analysis of mechanically compensated zoom lenses
Author(s):
Kazuo Tanaka
Show Abstract
It is analyzed a mechanically compensated zoom lens in which the second and fourth components are movable to attain zooming effects, while the first, third and fifth components are fixed during zooming. It is derived a set of quartic and two (or four) elements simultaneous zoom equations each of which simultaneously satisfies two paraxial conditions; continuous change of magnification (or focal length) and constant object-image distance. Analytical solutions are obtained together with an approximate zoom equation in the vicinity of a critical point and that near a singular point. Numerical example is added to show the effectiveness of the analysis.
Prism-based fiber optical refractometer sensor
Author(s):
L. M. Bali;
Atul Kumar Srivastava;
Rajesh Kumar Shukla;
Anchal Srivastava
Show Abstract
The new design for the prism based refractometer sensor presented here is characterized by its high sensitivity over a wide range of refractive indices of the ambient. The refractometer is more robust and user friendly than other such refractometers reported in literature.
Grazing incidence interferometry with the help of diffractive masters
Author(s):
Johannes Schwider;
Sven Brinkmann;
Roland Schreiner;
Thomas Dresel
Show Abstract
The test of rod-like technical objects can be carried out in grazing incident using diffractive optical elements as beam splitters and at the same time as generators for master wave fronts. The occurring interference patterns can be evaluated with the help of the well known phase shifting technique. Wave aberrations caused by the adjustment state of the test sample can be removed from the data set via least squares fitting a functional representing the wave aberrations due to misalignments.
Collimation testing techniques: a review
Author(s):
Rajpal S. Sirohi
Show Abstract
Collimation of beam is essential in long path interferometry otherwise significant measurement error may be introduced. Therefore, considerable efforts were spent in developing techniques of collimation testing. In laser interferometers, the source is effectively a point. However, its axial shift from the focus of the collimator introduces a curvature in the wave front and its lateral shift may introduce off-axis aberrations. Therefore, the objective is to place the point source at the focus of the collimator. This task is achieved by collimation testing techniques, which can be grouped under interferometry, shear interferometry, Talbot interferometry, and phase conjugate interferometry. We will discuss these techniques below.
Advances in vertical-cavity surface-emitting laser
Author(s):
Kenichi Iga;
Fumio Koyama
Show Abstract
The vertical cavity surface emitting laser (VCSEL) [lJ is meeting the 3rd generation of development in 1999 and the deadline of the S. Y. Wang's prophecy is approaching a few years ahead. Actually, it has been being applied into various optical systems such as optical networks, parallel optical interconnects, laser printers, high density optical disks, and so on. We like to review the progress of VCSELs in wide spectral ranges covered by various 111-V compound semiconductors. Some innovating technologies will be discussed.
Filtering techniques for optical pattern recognition
Author(s):
Philippe Refregier
Show Abstract
Optical pattern recognition and in particularly optical correlation has been the subject of intensive research for many years. The basic principle consists of the comparison of a reference image with the scene to analyze. The potential advantage of optical technologies is their ability to determine the conelation function very rapidly. Most of the research effort has concentrated on technology, and particularly on the spatial light modulators (SLM) which enable to encode the reference and the input images on a coherent optical beam and on the detectors. The recent availability of efficient SLM's and fast detectors has allowed the realization of different [1,2,3] optical correlator demonstrators and the question of their practical fields of applications becomes more stringent.
Performance progress of a human face recognition processor
Author(s):
Haisong Liu;
Minxian Wu;
Guofan Jin;
Qingsheng He;
Yingbai Yan
Show Abstract
This paper gives a concise summary on recent progress of our research on an incoherent optical correlator based optoelectronic human face recognition processor. Several methods for improving its processing speed, discrimination ability, and robustness are illustrated.
Detection of wood density by a diffractive-optics-based sensor
Author(s):
Raimo Veil Johannes Silvennoinen;
Jari Palviainen;
Seppo Kellomaeki;
Heli Peltola;
Kari Sauvala
Show Abstract
Wood quality is of great importance for all of forest industry, because it affects on suitability of wood as raw material for the wood processing industry. In the future, the aim will be to use the right materials for the right end products. For this purpose we need to understand how the material properties of wood are distributed in the stem, and how the properties of wood vary from a tree to tree and from a stand in relation to the genetics, site properties and silvicultural history. Currently, detailed information is lacking how genetic, environmental and forest management influence wood properties (i.e. between and within ring variation). This is although, for example, wood density and equally percentage of latewood, which is known to reduced by faster diameter growth, i.e. larger proportion of earlywood. Wood density reflects also the amount of cell wall material, and it is considered as a key property. It also correlates to other properties of the wood like strength (important for mechanical industry) and pulp yield in terms of the quantity of chemical and mechanical pulp obtained from the volume unit. For the pulp and paper industry, the earlywood/latewood ratio is respectively of great importance, because latewood tracheids of softwoods have thick walls, which increase the density and mechanical strength of wood. On the other hand, considerably more energy is needed in defibration of latewood than earlywood.
Multi-object intensity-invariant pattern recognition with an optimal processor for correlated noise
Author(s):
Rafal Kotynski;
Katarzyna Chalasinska-Macukow
Show Abstract
Normalized correlation provides a way to achieve reliable pattern recognition with images containing multiple target objects of unequal intensities without the need of image segmentation. We show that the optimum Bayesian processor for the detection of a target with additive correlated noise and disjoint background, introduced, has the form of the normalized correlation. In consequence it can be expressed with correlations and pointwise processing only--which is a condition for an efficient optical implementation. Moreover it may be applied to multi-object intensity invariant problems.
Diffraction by fractal apertures and Babinet's principle
Author(s):
L. Baum;
V. Laguna Weinberg;
J. Cesaretti;
J. A. Martinez;
Mario Garavaglia
Show Abstract
Babinet's principle establishes the equivalency from the diffracting fields by complementary gratings. In this work there is shown results obtained by the diffracting field of different orders of Cantor's and Sierpinski's Fractals and their complementary, according to Babinet's principle, observed experimentally and computer simulations. The agreement of results is excellent.
Fractal speckles in diffraction regions and image plane
Author(s):
Jun Uozumi;
K. Tsujino;
E. Miyasaka;
M. Ibrahim
Show Abstract
Speckle patterns having fractal properties are produced in the image plane as well as in the diffraction regions of a planar diffuser. Such a pattern has no definite speckle size and exhibits a statistical self-similar feature within a limited extent. The intensity correlation function is shown to obey a power-law, which is a typical property of fractal distributions.
Direct control of fractal pattern generation on optical fractal synthesizer
Author(s):
Toru Sasaki;
Jun Tanida;
Yoshiki Ichioka
Show Abstract
We propose a new method for direct control of position, rotation, and scaling of fractal patterns generated on the optical fractal synthesizer. In this method, we introduce IFS mother function to generate control parameters for arbitrary fractal patterns. We implemented the method experimentally and verified effectiveness of the method.
Design, figuring, and measurement of a correction plate for a wafer stepper
Author(s):
Denis A.M. Faas;
Cees J. Van Der Laan;
Joseph J. M. Braat;
Tark Wijchers
Show Abstract
A plate with constant thickness was designed to compensate for the residual distortion in the image projected by a high-quality projection lens for lithography. The two surfaces of the plate have an identical aspheric profile whose shape has been calculated using the measured distortion map of the lithographic objective. The figuring process applied to the plate uses the principle of polishing in the presence of an elastical deformation to achieve the desired aspheric shape on both sides. A description is given of the subsequent process steps and of the obtained surface accuracy.
Future of optical lithography
Author(s):
Shinji Okazaki
Show Abstract
The history of optical lithography is reviewed as a basis for discussing its future. The key methods used so far to boost the resolution are: the use of a higher numerical aperture, reduction of the exposure wavelength, and the introduction of resolution enhancement technologies. For the continued use of optical lithography in the future, the exposure wavelength must be reduced. The two approaches to doing this--a gradual reduction and a sudden, large reduction--are compared.
Balanced-homodyne detection of surface second-harmonic generation
Author(s):
Jun Chen;
Susumu Machida;
Yoshihisa Yamamoto
Show Abstract
An ac optical balanced homodyne detection system was developed to simultaneously measure the intensity and phase in surface second-harmonic generation. Extremely high sensitivity of 3 aW (6 photon/sec) has been achieved by use of a lock-in amplifier, in which an interference signal of fundamental waves is used as a reference signal. Experimental results of simultaneous measurement of the intensity and phase in surface second-harmonic waves generated form native-oxidized Si(111) surfaces is presented.
Optical nonlinearities in mesoionic compounds
Author(s):
Arandi G. Bezerra Jr.;
Anderson S. L. Gomes;
Glauco S. Maciel;
Cid B. de Araujo;
P. F. Athayde-Filho;
G. B. da Rocha;
J. Miller;
A. M. Simas
Show Abstract
Using the hyper-Rayleigh and the Z-scan techniques, we determined the first and the second hyperpolarizabilities of molecules containing mesoinic rings. We also present quantum chemical calculations for both hyperpolarizabilities that are in a good qualitative agreement with experimental results. Optical Kerr gate measurements indicate response times faster than 60 fs for these compounds which possess intrinsic push-pull characteristics and are promising substitutes for polyene bridges in photonic applications.
Guiding light by incoherent light
Author(s):
Zhigang Chen;
Mordechai Segev
Show Abstract
We demonstrate, for the first time, optical guidance of light beams using incoherent light. Such guidance is made possible by generating self-trapped dark beams (dark spatial solitons) inside a bulk photorefractive material using spatially incoherent light. We show that, in the 1D case, planar or Y-splitting waveguides induced by self-trapped incoherence dark stripes can guide other coherent light of a different wavelength. In the 2D case, incoherent dark solitons generated from optical vortices induce refractive- index changes akin to circular channel waveguides. These experiments introduce the possibility of controlling high- power laser beams with low-power incoherent light sources such as Light Emitting Diodes.
Generation of tunable coherent VUV/XUV radiation in molecules
Author(s):
Tao-Heng Sun;
Pengqian Wang
Show Abstract
We report the new results of continuously tunable coherent VUV/XUV radiation produced by twophoton resonantly enhanced third harmonic generation and four-wave sum-mixing in 2 , H2 , CO, and 4 molecules. By use of the radiation from molecules combine to the radiation generated from Xe, Kr, Ar, and Ne atoms we have developed a reasonably practical VUV/XUV tunable coherent radiation source. The theory analysis, experimental results, and the experimental system, as well as the key techniques are presented in this paper. There are many exciting applications of coherent vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) sources in photochemistry, material science, atomic physics, and life sciences, but to become practical, these applications require a convenient laser source that can be easily asembled and that can operate in the laboratory with a minimum of attention. We report the new results of the generation of tunable coherent VUV/XUV radiation by two-photon resonantly enhanced third harmonic generation (THG) and four-wave sum-mixing (FWSM) in N2, H2 , CO , and 4 molecules. By use of these radiation combine to the radiation generated from Xe, Kr, Ar, and Ne atoms which we have produced previously, a reasonably practical VUV/XUV tunable coherent source has been developed and sued to the applications. The system is described as follows, the pumped source is the pulsed dye laser pumped by Nd:YAG laser, which has a linewidth of about 0.1 cm -i, was frequency-doubled by a BBO crystal. The output of the BBO crystal, acting as the input beam, was focused into the center of a molecular gas beam which is provided by a pulsed gas jet. The generated radiation of the third harmonic and the four-wave sum-mixing were separated from the irput laser by a VUV monochromator and was detected by an electron multiplier. All the detail results including the generated VUV/XUV radiation spectrum will be presented in our report. Moreover, we calculated the two-photon resonant TH and FWSM intensity of these molecules, it shows that five branches, namely O,P,Q,R, and S branches can be produced from part of the molecules, but the Q branch usually has a very weak third order susceptibility, and the intensity of the other four branches are mainly . governed by the rotational population of the ground state. Due to the expansion cooling of the gas jet, the population is always concentrated on a few rotational levels of the ground state, thus only a few rotational lines can be obtained in each branch. As an example, we consider CO molecule and suppose J = 4 is the most populated level and the population has a Boltzman distrbution, the temperature of the gas beam at the laser focus is estimated to be I I OK . Thanks to the rotaional cooling effect, the TH spectrum is greatly simplified and the rotational lines can be easily assigned, and the intenensities of the resonant lines which have the optimum population can be significatly improved. Also the TH and FWSM conversion efficieny are found to be of the same order or a little smaller than that in a three-phton resonant THG process in inert gas, this proves that these molecules are an efficient nonlinear medium for generating bright, tunable coherent VUV/XUV radiation.
Experimantal studies of quantum cryptography in optical fiber communication systems
Author(s):
Nicolas Gisin
Show Abstract
Quantum mechanics is well known for being counter-intuitive or even bizarre. Now, it can also be useful for practical applications. Quantum cryptography could be the first application of quantum mechanics at the individual quanta level. It takes advantage ofthe Heisenberg uncertainties to provide an absolutely secure communication scheme.
Practical point-to-point free-space quantum key distribution over .5 km
Author(s):
William T. Buttler;
Richard J. Hughes;
Paul G. Kwiat;
Steve K. Lamoreaux;
George L. Morgan;
Jane E. Nordholt;
C. Glen Peterson
Show Abstract
We have demonstrated point-to-point single-photon quantum key distribution over a free-space optical path of approximately 475 m under daylight conditions. This represents an increase of > 1,000 times farther than any reported point-to-point demonstration, and > 6 times farther than the previous folded path daylight demonstration. We expect to extend the daylight range to 2 km or more within the next few months. A brief description of the system is given here.
Limits of light concentration and energy yield of luminescence
Author(s):
Christoph Zander;
Karl-Heinz Drexhage
Show Abstract
Taking the quantum nature of photons as well as the first and second law of thermodynamics into account as universal upper limit for the concentration of incoherent light is found. Furthermore the limitation of light concentration by a 4-energy-level system is investigated. It turns out that both considerations lead to the same limits. Furthermore the conditions for luminescence energy yield exceeding unity are laid down.
Phase-space tomography of the truncated harmonic oscillator states
Author(s):
Marta Cecilia Gonzalez;
Celso Luis Ladera
Show Abstract
Phase-Space Tomography has been recently applied, in complete analogy to classical optics tomography, for the reconstruction of quantum states. The quantum systems thus far considered move in potentials for which only the coordinates of phase space are modified by simple affine transformations--shearing and rotation--, the state Wigner quasi-probability distribution remaining invariant. In this work we consider the case of the truncated harmonic oscillator, a more general, and potentially useful, potential, and show that state reconstruction is still feasible.
Recovery of classical images and nontomographic quantum state reconstruction
Author(s):
Celso Luis Ladera
Show Abstract
Quantum tomography, as being recently used in atomic optics and quantum optics for quantum state recovery, has been developed in analogue fashion to the standard method of classical computer tomography. Unfortunately, it is only possible to handle a limited number of cases with such methods. Advanced non-tomographic quantum state reconstruction is now being developed as an alternative to achieve reconstruction for arbitrary potential functions. It has now become feasible, in turn, to apply the new method, again in analogue fashion, for the reconstruction of classical images.
Image reconstruction from its Fourier modulus
Author(s):
Tohru Takahashi;
Hiroaki Takajo
Show Abstract
An iterative algorithm to reconstruct an image from its Fourier modulus is proposed. Although this algorithm is a modification of the conventional iterative Fourier transform algorithm proposed by Fienup, stagnation which the conventional algorithm often suffers from does not occur in this algorithm.
Nonlinear optical element for incoherent image processing based on photoanisotropy
Author(s):
Burkhard Fleck;
Lutz Wenke;
P. S. Ramanujam
Show Abstract
Optical information processing is a very important branch of optics research nowadays. One interesting application is the comparison of two images. These techniques are of interest in many applications such as automatic inspection, remote sensing or in communication processing. Such a comparison by means of optical methods is a well established technique both for coherent and incoherent illumination and various methods are known. But especially the use of incoherent light is often connected with complex setups. We describe a simple method for a correlation technique based on optically induced anisotropy which allows the use of white light or of two mutually incoherent laser beams. The element based on the specific feature of photoanisotropic media. These materials response on the intensity of a linearly polarized light wave only.
Speckle photography through different multiaperture pupils
Author(s):
Luciano Angel;
Myrian C. Tebaldi;
Nestor A. Bolognini;
Marcelo Trivi
Show Abstract
An image multiplexing method based on the internal modulation of speckle grains by employing different multiple aperture pupils for recording is proposed. The interferometric fringes profile and visibility in the Fourier plane, for uniform in-plane displacement double- exposed specklegrams through different pupils recording, are analyzed in terms of the geometric parameters of the pupils. Experimental evidences are presented.
Imaging interferometric lithography: extending optics to fundamental limits and beyond
Author(s):
Steven R. J. Brueck
Show Abstract
Optical lithography has been the mainstay VLSI/ULSI manufacturing technique throughout the entire history of the integrated circuit. The "end" of optical lithography has been oft predicted, and just as often proven premature. Even today, despite all the recent investigation of next-generation lithographies (NGL), it now appears certain that optics will be used for 100-nm critical dimensions (CD) and likely, that optical tools will extend at least to initial stages of the 70-nm CD roadmap node as well, cxtending optical lithography to deep sub-wavelength CDs.
Resonator-configuration-dependent nonlinear dynamics with application to Kerr-lens mode-locked lasers
Author(s):
Wen-Feng Hsieh;
Ming-Dar Wei;
Hsiao-Hua Wu
Show Abstract
The nonlinear dynamics of the Gaussian beam propagation in resonator was studied by constructing the iterative map of q-parameter. From the Greene's residue theorem, there are specific configurations sensitive to nonlinear effect existing in the geometrically stable region. By applying to Kerr-lens mode-locking (KLM) resonators, we found that multiple solution, period doubling, period tripling and period quadrupling can occur at the configurations with product of cavity G-parameters equal to 0, 1/2, 1/4 (or 3/4) and (2 +/- yields2)/4, respectively. Moreover, the systems will result in classical chaos if further increasing the nonlinear effect. We will also report appearance of unexpected transverse beam profiles and shrinkage of beam waist causes to lower laser threshold in an end-pumped Nd:YVO4 laser and chaotic behavior in the KLM laser around these critical resonator configurations.
Self-modulation of pulses in Kerr medium and limits of the single-mode approximation
Author(s):
Dmitri Kouznetsov;
Eduardo Gomez
Show Abstract
Any nonlinear interaction, in principle, can produce non-classical state. The Kerr nonlinearity seems to be the simplest one. Since papers [1-3], it seemed that as the squeezed states, as the Schriidinger cat ones can be produced by the self-modulation. The squeezing was really observed [ 3] in such a scheme. As for cats, Ref. {4,5] mention the large distance of propagation and linear absorption as factors which make the experimental realization unlike. Note that neither the large distance of propagation nor the linear absorption are fundamental reasons why the Schrödinger cat cannot be obtained by such a manner.
Self-phase modulation of incoherent nonstationary pulses
Author(s):
Solange B. Cavalcanti;
M. Yu;
Govind P. Agrawal
Show Abstract
Propagation of partially coherent pulse trains in single- mode optical fibers is considered within the framework of the nonlinear Schrodinger equation. Statistical properties of chaotic modulated pulses are evaluated by modelling them after cyclostationary processes. Interesting spectra are obtained exhibiting the influence of self phase modulation on these random signals.
Thermal-lens measurements of thermal diffusivity temperature dependence up to the glass transition in a fluoride glass
Author(s):
S. M. Lima;
Tomaz Catunda;
R. Lebullenger;
Antonio Carlos Hernandes;
Mauro L. Baesso;
A. C. Bento
Show Abstract
The time-resolved mode-mismatched thermal lens technique has been used to determine the thermal diffusivity, D, temperature behavior of a fluoride glass (ZBLAN) from 25 to 315 degree(s)C. We observed an abrupt decrease on D with minimum at 298 degree(s)C which coincides with the glass transition temperature Tg value measured by DSC. These measurements indicate that the thermal conductivity, K, decrease by factor approximately 8.
CW optically pumped FIR waveguide lasers and harmonic mixing with Schottky diodes
Author(s):
Er Jun Zang;
Kun Zhao;
Xizhi Li;
Yuqing Zhou;
Baoqing Zhou;
Xuchang Gu;
Hongjun Cao;
Nai-Cheng Shen
Show Abstract
A CW optically pumped FIR waveguide laser is demonstrated. An output power of 75 mW at wavelength of 96.5 micrometers has been obtained and harmonic mixing between microwaves and FIR radiation has been shown.
Achromatization of the diffraction efficiency of diffractive optical elements
Author(s):
Kenneth J. Weible;
Andreas Schilling;
Hans Peter Herzig;
Daniel R. Lobb
Show Abstract
Diffractive optical elements (DOEs) are characterized by a large negative dispersion. This property can be exploited to correct chromatic aberration in hybrid optical systems. The diffraction efficiency of phase DOEs decreases when the wavelength deviates from the design wavelength. Consequently, DOEs are usually applied only in optical systems where the spectral bandwidth is limited. Thus the dilemma that the chromatic correction capability of the DOE can not be fully exploited in optical systems with large spectral bandwidths where the correction could be most useful. It has been shown that by careful selection of the dispersion properties of two different optical materials it is possible to achromatize the diffraction efficiency of the DOE in a sandwich configuration, Fig. la.1 The dispersion properties of the two materials must be matched such that refractive index change at the interface, An(2), remains proportional to the wavelength, A, i.e.AIzn() = constant. The introduction of a second surface profile removes the above constraint on the dispersion properties of the materials. Such an approach has been described where an air gap has been inserted between the two materials and the depth of the surface profile for each material are optimized to minimize the variation of the phase modulation with wavelength, Fig. lb.2 Better performance can be achieved by placing the second surface relief on the exterior of one of the sandwiched materials, Fig. ic. The advantages are reduced shadowing effect, less Fresnel reflection losses, and much better fabrication tolerances. Furthermore, the second surface profile has removed the materials limitation. Materials that are much better suited to fabrication can be used, thus allowing for mass fabrication at reduced costs.
Computer-generated diffractive laser beam splitter
Author(s):
Dan Cojoc;
Octavian Dontu
Show Abstract
A technique to obtain a diffractive laser beam splitter is presented in this paper. The technique is based on the approach of Fresnel holography, computer generated. Starting from the coding techniques used to obtain binary Fresnel encoded lens and Fresnel holograms, the synthesis of a diffractive optical element able to realize the split of a laser beam into N beams, is presented. Experimental results are provided for N equals 2, 3, 4, 5. The performance of this beam splitter is discussed in terms of light transmission efficiency and reconfigurability.
Diffractive optics in physical-optics system design
Author(s):
Frank Wyrowski;
Jari Pekka Turunen
Show Abstract
The use of microstructured interfaces to realize optical functions is the subject of diffractive optics. In this talk we discuss the role of diffractive optics in optical engineering. To this end optical design is based on a physical-optics model. It is established that microstructures can present alternative ways to realize optical functions and that they can be the ultimate choice to obtain a desired optical effect.
Detection and identification of single molecules in microcapillaries
Author(s):
Christoph Zander;
Karl-Heinz Drexhage
Show Abstract
A set-up permitting optical detection and identification of individual analyte molecules (dye labeled mononucleotides) in microcapillaries is described. It consists essentially of a confocal fluorescence microscope for time-correlated single-photon counting. Excitation of the analyte molecules takes place in the red spectral region with a short-pulsed diode laser at about 640 nm. A cone shaped capillary with an inner diameter at the very end of about 0.5 micrometers was used. The flow of the labeled nucleotides was established by electrokinetic forces. A maximum likelihood estimator was applied to analyze the measured fluorescence decays of the analyte molecules. This way two species of labeled mononucleotides can be distinguished by their characteristic fluorescence decay time on the single-molecule level.
New dynamic endoscopic holographic interferometer for in-vivo medical imaging metrology
Author(s):
Gert von Bally;
Bjorn Kemper;
Andre Merker;
S. Lai
Show Abstract
A novel Electronic-Speckle-Pattern-Interferometer which is based on an endoscope camera system can be applied to handheld examinations for in-vivo minimal-invasive diagnostics. Optical fibers, endoscopic optics and an amplitude modulated cw-laser are used for illumination. A CCD-camera in combination with a fast frame grabber-system allows dynamic `on line'-image subtractions up to a frequency of 25 Hz with high fringe contrast. The influence of rigid body motions on the interference fringe pattern is compensated by a new digital processing method based on Fourier algorithms.
Pathogen detection using evanescent-wave fiber optic biosensor
Author(s):
Aldo Pacheco Ferreira;
Marcelo Martins Werneck;
R. M. Ribeiro;
U. G.C. Lins
Show Abstract
This paper describes a real time optical biosensor that utilizes the evanescent field technique for monitoring microorganisms in hospital environment. The biosensor monitors interactions between the analytic (bacteria) and the evanescent field of an optical fiber passing through the culture media where the bacteria grows. The objective is to monitor atmospheres in hospital areas for the Staphylococcus aureus and Streptococcus pneumonia. The results lead us the conclusion that this kind of sensor presents quick response, good performance, easy of construction and low cost. We expect that the sensor will be of great help in controlling the hospital environment.
Biomedical applications of laser spectroscopy
Author(s):
Sune Svanberg
Show Abstract
Very soon after the invention of the laser, the use of the thermal effects of the radiation was introduced. Such techniques have been refined and the laser is now routinely used for treatment in many specialities. Photodynamic therapy (PDT) is a non-thermal modality employing the combination of a tumor-seeking agent and activating laser light. During the last 15 years laser spectroscopic techniques have also been developed providing powerful means for non-intrusive medical diagnostics of tissue in real time. At the beginning only few groups were involved in exploratory work, but successively the field has developed now to occupy a large number of research teams, which meet at large specialized conferences. We will here consider three aspects of laser diagnostics: fluorescence, Raman and near-IR, and elastic scattering spectroscopy, and we will also briefly discuss PDT. The activity in the field is very extensive, and rather than trying to give a full overview, illustrations from work performed at the Lund University Medical Laser Center will be given.
Spatio-spectral tomography of luminescent objects with volume holograms
Author(s):
George Barbastathis;
David J. Brady
Show Abstract
Volume holograms as optical imaging elements provide maximum flexibility in the design of the optical response. For example, when a polychromatic incoherent object illuminates a spherical-reference volume hologram, the shift selectivity effect extracts only a color-dependent slice of the object, which is reconstructed on a planar detector. In this presentation we characterize the performance (resolution and dynamic range) of a tomographic imaging system based on this effect.
Biomedical imaging using optical coherence tomography
Author(s):
James G. Fujimoto
Show Abstract
Optical coherence tomography (OCT) is a recently developed optical imaging technique that performs high resolution, cross-sectional tomographic imaging of microstructure in biological systems. OCT is analogous to ultrasound B mode imaging except that it uses light instead of sound. OCT performs imaging by using low coherence interferometry to measure the optical backscattering of tissue as a function of echo delay and transverse position [1]. The resulting two-dimensional data set can be displayed as a gray scale or false color image. OCT functions as a type of "optical biopsy" to provide cross sectional images of tissue structure on the micron scale. OCT is a powerful imaging technology because, unlike conventional histopathology, which requires removal of a tissue specimen and processing for microscopic examination, OCT can provide images of tissue in situ and in real time, without the need for excision. OCT has originally been developed and applied by our group for tomographic diagnostics in ophthalmology [2,3]. OCT can provide images of the retina with resolutions of 10 p,m, one order of magnitude higher than conventional ultrasound. Working in collaboration with the New England Eye Center and MIT Lincoln Laboratory, we have developed a clinical prototype OCT instrument and examined over 5000 patients. The technology has been transferred to industry, and a commercial product was introduced into the ophthalmic market in 1996. Studies in ophthalmology show that OCT is especially promising for the diagnosis and monitoring of diseases such as glaucoma or macular edema associated with diabetic retinopathy where it provides quantitative information on disease progression. In many cases OCT has the ability to detect and diagnose early stages of disease before physical symptoms and loss of vision occur. Recent research on OCT has focused on developing technology to perform optical biopsy in internal medicine [4-6]. OCT at optical wavelengths in the near infrared where tissue scattering is minimized allows imaging to be performed to depths of 2-3 mm. Using solid state modelocked laser sources which can provide both short coherence lengths and high powers, high resolution and high speed imaging may be achieved. Image resolutions of 5-10 im and high speed acquisition of 250 x 250 pixel images at rates of 8 frames per second have been achieved. OCT imaging has been integrated with microscopy to perform imaging of specimens in vitro. A prototype single mode fiber optic catheter/endoscope with a diameter of 1 mm has been developed which can transluminally image internal tissue structures such as the respiratory tract, gastrointestinal tract, or arteries. In recent studies, catheter/endoscope based OCT imaging of internal organs in an animal model has been demonstrated [7]. Endoscopic OCT imaging in patients has also been demonstrated [8]. Ultrahigh resolution OCT has recently been developed and demonstrated. Kerr lens modelocked Ti:sapphire lasers have achieved sub-two cycle duration optical pulses with a corresponding bandwidth from 650 nm to 1000 nm [9]. Since the axial resolution of OCT is inversely proportional to the bandwidth of the light source, axial resolutions of 1 -2 im can be achieved. A novel C-scan focus tracking and image fusion technique has also been demonstrated to overcome depth of field limitations and permit 3 im transverse resolutions. This system can achieve subcellular level resolution and promises to be a powerful research tool in developmental biology and future clinical studies [10]. OCT is a promising and powerful medical imaging technique because it can permit the in situ visualization of tissue microstructure without the need to remove a specimen excisionally as in conventional biopsy and histopathology. The concept of nonexcisional "optical biopsy" provided by OCT and the ability to visualize tissue architectural morphology in real time under operator guidance can have many applications in several scenarios: 1) For situations where conventional biopsy is either hazardous or impossible, 2) Where biopsy has an unacceptably high false negative rate due to sampling errors, and 3) For guiding surgical intervention. This presentation will discuss technology and applications of this new imaging modality.
Imaging of the static and dynamic objects by pulse super-scanning locator (SSL) (tomograph) with resolution higher than by the Rayleigh criterion
Author(s):
Vera Moiseevna Ginzburg
Show Abstract
Results of theoretical and experimental research to develop a locator (tomograph) with antenna performing beam scanning during both the emission and reception of pulses are presented'3. The locator operation is illustrated in Fig. 1 . The antenna having the angular beam width e0 emits pulses over the given surveying angle ® with duration t and repetition period T. Having emitted the pulse, the antenna rapidly regains the initial orientation and after a time delay of td resumes scanning over the sector ® according to the same (or different) scanning law. The emitted energy occupies in space a confmed section in the form of Archimedes (Fig. ic) spiral having the thickness c; c'r (e/®). The energy reflected from an object comes back in the shape of spherical layer. It can be totally received only when antenna beam is directed at the same angle as at the initial moment of signal transmission. As a result, the reflected signals are received from certain visibility layers VLs (Fig. ld) with the depth 6R= c-rI2 and repetition period AR =c(t + tr)12, where r is the reverse travel time of the beam forming the inclined visibility layers. By using different antenna scanning laws, a surveying net can be formed in space (see Fig. 1 e).
Multiple-component laser Doppler velocimeter using a chirp-frequency-modulated Nd:YAG ring laser and fiber delay lines
Author(s):
Juergen W. Czarske;
O. Doelle;
Ingo Freitag;
Carsten Fallnich
Show Abstract
A 2D directional laser Doppler velocimeter (LDV), which is based on the generation of heterodyne signals of different carrier frequencies, so that different velocity components can be detected simultaneously will be presented. The carrier frequencies are generated by a chirp frequency modulation of a diode-pumped monolithic Nd:YAG miniature ring laser in combination with fiber delay lines of a few 100 m lengths. Since this heterodyne technique is based on a complete spliced fiber optic unit without additional frequency shift elements, a simple alignment-insensitive heterodyne LDV system can be realized. Together with the Nd:YAG laser, emitting about 1 W single-frequency power, a portable powerful LDV was realized. The generated LDV signals are evaluated by the quadrature demodulation signal processing technique, which allows the measurement of the Doppler frequency with a high time resolution. As a result, frequency modulated LDV signals, e.g. from sound waves or turbulent flows, can be evaluated.
Application of solid-immersion lens technology to optical storage (Abstract Only)
Author(s):
Gordon R. Knight
Show Abstract
Solid Immersion lens technology was originally discovered for microscopy. In the past few years significant investments in this technology have been made for the purposes of optical data storage. The advantages and challenges of SIL technology for storage applications will be discussed, including the effects of evanescent coupling, media layer structure, and lens material selection on aerial density and signal-tonoise ratio. Experimental results for recording at high densities with a SIL based drive system will be presented.
Quantum state reconstruction and optimal manipulations with quantum information (1996 IOC Prize Winner)
Author(s):
Vladimir Buzek
Show Abstract
The concept of a quantum state represents one of the most fundamental pillars of the paradigm of quantum theory.'3 Contrary to its mathematical elegance and convenience in calculations, the physical interpretation of a quantum state is not so transparent. The problem is that the quantum state (described either by a state vector, or density operator or a phase-space probability density distribution) does not have a well defined objective status, i.e. a state vector is not an objective property of a particle. According to Peres (see,1 p. 374): "There is no physical evidence whatsoever that every physical system has at every instant a well defined state. .. In strict interpretation of quantum theory these mathematical symbols [i.e., state vectorsi represent statistical information enabling us to compute the probabilities of occurrence of specific events." Once this point of view is adopted then it becomes clear that any "measurement" or a reconstruction of a density operator (or its mathematical equivalent) can be understood exclusively as an expression of our knowledge about the quantum mechanical state based on a certain set of measured data. To be more specific, any quantum-mechanical reconstruction scheme is nothing more than an a posteriori estimation of the density operator of a quantum-mechanical (microscopic) system based on data obtained with the help of a macroscopic measurement apparatus.3 The quality of the reconstruction depends on the "quality" of the measured data and the efficiency of the reconstruction procedure with the help of which the data analysis is performed. In particular, we can specify three different situations. Firstly, when all system observables are precisely measured. In this case the complete reconstruction of an initially unknown state can be performed (we will call this the reconstruction on the complete observation level) . Secondly, when just part of the system observables is precisely measured then one cannot perform a complete reconstruction of the measured state. Nevertheless, the reconstructed density operator still uniquely determines mean values of the measured observables (we will denote this scheme as reconstruction on incomplete observation levels) . Finally, when measurement does not provide us with sufficient information to specify the exact mean values (or probability distributions) but only the frequencies of appearances of eigenstates of the measured observables, then one can perform an estimation (e.g. reconstruction based on quantum Bayesian inference) which is the "best" with respect to the given measured data and the a priori knowledge about the state of the measured system.
Superradiant effects in the active microcavity
Author(s):
E. De Angelis;
Francesco De Martini;
Paolo Mataloni
Show Abstract
The process of two-dipole superradiance has been investigated by femtosecond excitation of two ensembles of dye molecules, located at a mutual distance R on the symmetry plane of a microcavity. In these conditions, superradiant coupling between the two objects can be established, giving rise to emission correlation effects, which have been investigated in the space-time domain.
Suppression of closed-loop photocurrent fluctuation below amplifier dark noise
Author(s):
Jianping Yin;
Weijian Gao;
Yifu Zhu;
Yuzhu Wang
Show Abstract
Suppression of the closed-loop photocurrent fluctuation below the amplifier dark noise was observed in both a negative-feedback light-emitting diode and a laser diode. We apply the concept of an anticorrelation light state proposed by Masalov et al to analyze the anticorrelation effect between the measured photocurrent fluctuation and the amplifier dark noise, which successfully explains our experimental observations. Our theoretical analysis also yields the squeezed spectrum of the light intensity fluctuation in the loop and the correlation coefficient between the photocurrent and the amplifier noise.
Continuous measurement of photon number with double registration of counts
Author(s):
Antonin Luks;
Vlasta Perinova
Show Abstract
We investigate the role of stable atomic states in the microscopic theory of continuous quantum-nondemolition measurement of photon number. Conventionally, their energies are equal. When the stable states correspond to different energy levels, the measured mode is effectively incoherently coupled to another mode.
Two-wavelength interferometry based on a Fourier-transform technique
Author(s):
Ribun Onodera;
Yukihiro Ishii
Show Abstract
Two-wavelength interferometry that is based on a Fourier- transform technique has been investigated. A phase profile at a synthetic wavelength has been obtained by the inverse Fourier transformation of a first-order frequency spectrum for (lambda) 1 wavelength and a minus first-order frequency spectrum for (lambda) 2 wavelength. A power- spectrum of the two-wavelength interferogram can be controlled to eliminate a phase error caused by the difference between modulation intensities at two wavelengths.
Birefringent scatterplate phase-shifting interferometer
Author(s):
Michael B. North Morris;
Jay Van Delden;
James C. Wyant
Show Abstract
A new phase shifting scatterplate interferometer is realized by exploiting the polarization characteristics of a birefringent scatterplate. The advantages of this design are that it does not require any optical components to be placed near the surface under test and, the hot spot and background intensity, which are inherent to scatterplate interferometers, are eliminated. The theory of the interferometer is presented.
Phase-shifting digital holography with applications to microscopy and interferometry
Author(s):
Ichirou Yamaguchi
Show Abstract
Holography enables recording of full information from three-dimensional (3-D) objects on a hologram and to reconstruct wave propagation from the hologram. One of the issues in conventional holography is time and trouble of photographic recording of holograms. Furthermore, the reconstructed images are often taken by a CCD camera followed by a computer that extracts quantitative information. Digital holography that uses recording of holograms by a CCD camera and image reconstruction by a computer realizes direct acquisition of 3-D information and derivation of required quantities. It has become more practical owing to recent advances in CCD's and computers. The earlier digital holography used off-axis setups and the wanted reconstruction is always accompanied by the zero-order and the conjugate images1'2. We got rid of this limitation by introducing phase-shifting technique by which the distribution of complex amplitude at the hologram plane can be directly denved3. We applied this technique to 3-D microscopy4 and analysis of phase objects. This presentation summarizes their main results.
New Fourier transform profilometry based on modulation measurement
Author(s):
Xianyu Su;
Likun Su;
Wansong Li
Show Abstract
This article propose a new Fourier transform profilometry based on modulation measurement. We briefly call it FTP based on MM. Its main advantage is that it can measure the surface of a complex object in the same direction of projecting light, so it has no the difficulties due to shadow and spatial discontinuity that exist in conventional FTP and also PMP methods. In the paper, we give the principle of the method, the set-up of measurement system, and some primary experimental results. The results proved that this method is a promising method for acquiring 3D data of complex object.
Three-dimensional optics for optical data storage and optical MEMs using two-photon technology
Author(s):
Satoshi Kawata
Show Abstract
The lemtosecond laser technology is successfully combined with the laser-scanning microscope technology to OI)Cfl up the new world of three-dimensional microscale optics. We have proposed the use of Iemtosecond micro-structure in photopolvmerizahle resin[ 1. 2. Figure 1 shows a collection of photographs ol microstruCtureS made by a laser. Micron scale tube, coil, and funnel are solidified in photopolymerizable resin as a focused beam of infrared pulse laser runs three dimensionally in the resin according to the computer-programmed sequence. Only the beam focus where photon density is high enough. two photons of near infrared are coherently absorbed by the ultraviolet-sensitive photopolymerizable monomer/oligomer. resulting in local solidification of resinlSee Fig.2. The structure is extracted from the resin by removing unsolidified resin with ethanol. To enhance the square law in intensity of two-photon process, a high peak OWCF during the pulse is required for laser, while the mean power should he moderate. We used a Titanium Sapphire laser at 7)0nm with l6Ofsec with the peak power of 50kw. Figure 3 shows the absorption spectrum of the resin (SCR-500: Japan Synthetic Rubber Co.. Ltd.) which we used.
Two-photon multilayer bit data storage by use of continuous-wave illumination
Author(s):
Min Gu;
Daniel Day
Show Abstract
A continuous wave laser beam of an infrared wavelength at 800 nm is used for two-photon excitation in a photobleaching polymer for 3D bits data storage. We successfully demonstrate the recording and reading of multiple layers of data bits up to a depth of 100 micrometers within a thick photobleaching polymer. The achievable 3D bit density may be up to 3.5 Tbits/cm3 if a variable tube length can be implemented into the recording and reading processes.
Self-developing photopolymer system: an experimental investigation
Author(s):
Rene M. Beaulieu;
Roger A. Lessard;
Michel Bolte
Show Abstract
Dichromated poly(acrylic acid) (DCPAA) films have been investigated as photopolymer recording material. Thin DCPAA films with dimethylformamide have been used to photofabricate surface relief groups. The formation of these gratings depends on the self-development time in darkness subsequent to the illumination at the wavelength of 442 nm and is obtained without any chemical treatment or wet processing. In this experimental investigation, the effect of light exposure, heat treatment, and pH solution on the holographic characteristics of these gratings is studied.
Information storage with a barium-calcium titanate crystal
Author(s):
Matthias Esselbach;
Armin Kiessling;
Richard M. Kowarschik
Show Abstract
Barium-calcium titanate is a novel photorefractive crystal for optical storage applications. It is grown from a congruently melting composition from BaTiO3 and CaTiO3. In contrast to pure BaTiO3 the melting temperature is with I 592 °C nearly 30 ° deeper, the crystal is cubic at the growth temperature and shows a phase transition to the tetragonal structure at 98°C. It means that as in BaTiO3 a spontaneous poling appears. The lattice constants are smaller than in BaTiO3, a =b = 3.962 nm and c =3.999 nm and decreace with increasing Ca content. Therefore, the crystal is an optical uniaxial one. Asecond phase transition like in BaTiO3 is not found /1/. The refractive indices are slightly smaller than those of BaTiO3 but the electrooptic coefficients r13 =36 pm/V and r33 = 140 pm/V are larger (2 = 514 nm) /2/. Therefore, the BaiCaTiO3-crystal is a very promising material for optical information storage. In our experiments we used a 1 cm 1 cm 1 cm large crystal, poled in an external electric field, therfore obtaining a single domain sample. All sides are polished to optical quality. The sample shows in ordinarily polarized light extremly high fanning effects. We have studied the two wave mixing (TWM) for ordinary and extraordinary polarized light (A =514 nm). As expected, with extraordinary polarized light the buildup time is much longer (about 10 s) than with ordinarily polarized light (5 s), but the reached gain for a given intensity ratio between pump wave and signal wave is 2 orders higher. Varying the intensity ratio the logaritmic dependence of the gain on the intensity ratio is nearly linear. (The maximum value reached in our experiments is 4.6, it means the signal intensity behind the crystal is 40 000 times higher than the incident signal intensity). Very interesting is the behavior that the amplification will allways reach a maximum absolute value - nearly 3% of the pump wave is coupled to the signal wave. Reading the refractive index grating in the crystal after switching off the signal wave, a typical temporal behavior ofthe reconstructed signal wave is observed. This behavior can be explained with a multi level model ofthe photorefractive process inside the crystal /3, 4, 5/ The information will be recorded over a very long time interval, and multiple storage (for example via angular coding) is possible.
Visibility factor for low-particle-size polydispersity
Author(s):
Jose M. Saiz;
J. L. de la Pena;
Pedro J. Valle;
Francisco Gonzalez;
Fernando Gracia Moreno;
Gorden W. Videen
Show Abstract
We have developed an experimental light-scattering method to obtain information about particles with low polydispersities in size on flat substrates. It is based on the analysis of the visibility factor of the lobes in the light scattering patterns obtained from flat metallic substrates seeded with the particles. The visibility factor of a pattern is obtained for different minima. The solution of the scattering problem may be provided by a theoretical model, and analytical expressions for the visibility are derived. This relation between visibility and polydispersity is experimentally tested, and it is shown how the origin of the loss of visibility may be exploited to characterize the polydispersity.
Nanoparticle size distribution measurement in photon correlation experiments
Author(s):
Peter Jani;
Attila Nagy;
Aladar Czitrovszky
Show Abstract
We propose the measurement of particle size, which is based on the visibility measurement of the pre-detection signal corresponding to particle transit of the sensing volume in a photon correlation LDA arrangement. It is shown that a good estimate of the visibility is the ratio of the contents of two specific channels of the Fourier transform of the autocorrelation function. We show that in a wide range of experimental conditions this ratio is a monotonous function of particle size. This circumstance leads to the possibility of defining calibration curves for practical devices.
Polarized phase detection of optical beat signals for particle analysis
Author(s):
Naomichi Yokoi;
Yoshihisa Aizu;
Hiromichi Mishina
Show Abstract
A new technique based on the polarized phase detection of optical beat signals is proposed for size analysis of moving spherical particles. Light scattered by a particle in the two-beam intersection is divided into two rays and detected with different polarization angles. The phase difference between two beat signals can be used for particle size analysis. Numerical computations of the Mie theory and experiments were performed to verify the usefulness of the proposed technique.
Geometric phase coherence probe microscope for surface profiling
Author(s):
Maitreyee Roy;
L. Cherel;
Colin J. R. Sheppard
Show Abstract
We have developed a computer-controlled coherence probe microscope which can rapidly and accurately map the shape of micro-machined surfaces exhibiting steps and discontinuities. The instrument uses white-light and scans the object in height. The novel feature of the instrument is the use of an achromatic phase-shifter operating on the principle of geometric phase to evaluate the fringe visibility directly for each point on the object. This allows location of the position of the visibility peak along the scanning axis, yielding the height of the surface at the corresponding points.
Phase jump under surface plasmon resonance and its use for biosensing and microscopy
Author(s):
Petr I. Nikitin
Show Abstract
Interferometry that detects phase jumps of a beam reflected under surface plasmon resonance (SPR) has been developed for bio- and chemical sensing and microscopy. In our approach the near-field of surface plasmon is used to detect monolayer reactions on a metal surface or to visualize ultra-thin films. Comprehensive theoretical model and its experimental verification are presented. A number of prospective device schemes has been developed that provide sensitivity much higher as compared to the traditional SPR sensors and equally wide dynamic range. The proposed technique has been used for a `phase jump' SPR microscopy. It can also be used for Gene Chips and High Throughput Screening analyses.
Stroboscopic phase-shifting interferometry for dynamic characterization of optical MEMS
Author(s):
Matthew Richard Hart;
Robert A. Conant;
Kam Y. Lau;
Richard S. Muller
Show Abstract
Macro-scale optical components with surface flatness better than 25 nm over large areas (more than 1 X 1 mm) are widely available. However, the flatness of optical MEMS devices (for example micro-mirrors and -diffraction gratings) is often considerably worse. In addition to static deformation caused by film stresses and stress gradients, dynamic mechanical effects, such as air drag and excitation of higher-order resonant modes, cause surface deformations that are difficult to predict using theoretical or finite- element models. These deformations can cause significant degradation to optical performance. Dynamic measurements of nanometer-scale displacements across the entire surface of a micro-mirror are difficult or impossible to perform with conventional MEMS metrology techniques such as SEM, AFM, and optical microscopy. Stroboscopic interferometry, however, can be used to measure time-slice images that show 3D motion of fast-moving MEMS devices, with vertical resolution better than 1 nm. In this paper, we report the application of this technique to dynamic characterization of fold-up surface- micromachined structures and show how the method can be used to provide new insights into the optical and mechanical behavior of scanning micro-mirror devices.
Integrated micromachined scanning display systems
Author(s):
Paul M. Hagelin;
Uma Krishnamoorthy;
Robert A. Conant;
Richard S. Muller;
Kam Y. Lau;
Olav Solgaard
Show Abstract
We describe a raster-scanning display system comprised of two tilt-up micromachined polysilicon mirrors that rotate about orthogonal axes. We have demonstrated a resolution of 102 X 119 pixels. The optical efficiency of our two- mirror micro-optical raster-scanning system is comparable to that of micromachined display systems developed by Texas Instruments and Silicon Light Machines. Ease of integration with on-chip light sources and lenses has the potential to reduce packaging size, complexity and cost of the display system and makes it well suited for head-mounted display applications.
Near-field nano-optics toward nano/atom deposition
Author(s):
Motoichi Ohtsu
Show Abstract
Chemical vapor deposition by UV-optical near field realized a 20 nm Zn stripes, two closely spaced Zn dots, and a ZnO dot with light emitting capability. Optical switching capability of a single InGaAs quantum dot was confirmed by near-field nonlinear absorption spectroscopy. Recent progress of atom manipulation for deposition is also reviewed.
Fresnel diffraction experiments using coherent x rays
Author(s):
Jose Baruchel;
Peter Cloetens;
Jean-Pierre Guigay;
Michel Schlenker
Show Abstract
The new third-generation synchrotron facilities, which are in operation since a few years, provide X ray beams of high intensity, of small angular aperture (of the order of 0. 1 mrad) and high coherence properties, in comparison to more conventional X-ray sources. On some beamlines, the distance from the source to the object may be very large ; this distance is 150 meters on the 1D19 beamline at the ESRF; taking into account the source size s —50 and 150 im in the vertical and in the horizontal directions respectively, we obtain, for a wavelength = 1 A, a transverse vertical coherence length of 300 im and an horizontal one of 100 jim. By using a perfect crystal monochromator, a quasimonochromatic beam, with a relative wavelength spread A7J? iO ,is obtained.
Optimal phase mask for writing fiber Bragg gratings
Author(s):
Yue Qiu;
Yunlong Sheng;
Peter Kung
Show Abstract
The rigorous coupled-wave analysis and our experimental measurements show optimal values of the phase retardation and duty cycle of the phase mask to minimize zero and even diffracted orders, that are more precise than that usually used according to the scalar theory of diffraction. Under an oblique incidence, we optimize the phase mask with three parameters: phase retardation, duty cycle, and refractive index, that results in a perfect sinusoidal interference field with high diffraction efficiency for writing the fiber Bragg grating.
Combination of polarization-sensitive single-order and zero-order gratings
Author(s):
Tilman Glaser;
Ruediger Poehlmann;
Siegmund Schroeter;
Hartmut Bartelt
Show Abstract
We report on the simulation and experimental realization of two consecutive binary high spatial frequency gratings with high aspect ratios on the front and back faces of one fused silica substrate as polarization elements for visible laser light. The combination of rigorous coupled wave analysis and scalar decomposition of the incident Gaussian beam into a spectrum of plane waves results in good agreement between calculations and measured polarization properties.
Scanning near-field optical microscopy: local probes and enhanced electromagnetic fields
Author(s):
L. Aigouy;
Albert Claude Boccara;
S. Ducourtieux;
S. Gresillon;
Jean-Claude Rivoal;
Haim Cory;
Patrice Gadenne;
Vladimir M. Shalaev
Show Abstract
Enhanced electromagnetic fields are investigated, both theoretically and experimentally, on two model systems using high spatial resolution. Strong field enhancements at the apex of a tungsten tip illuminated by an external light source are studied as a function of the incident polarization. The surface of percolating random metal- dielectric films consist of several spectral resonances, which have been calculated and are observed here in near field with 10 nm lateral resolution.
Coherent anti-Stokes Raman scattering microscope
Author(s):
Mamoru Hashimoto;
Tsutomu Araki
Show Abstract
We propose a new laser scanning microscope using coherent anti-Stokes Raman spectroscopy. As the proposed method is a kind of Raman spectroscopy, molecular structural information are obtained without any staining. The imaging property is theoretically estimated by using the 3D optical transfer function. It is shown that the proposed microscope has 3D resolution in any case of measuring for the weak or the high contrast object with or without a pinhole before a detector. Spatial resolution of micrometer order along the optical axis is demonstrated.
Dynamic wavefront control in confocal microscopy
Author(s):
Tony Wilson;
Mark A. A. Neil;
Martin J. Booth
Show Abstract
We describe a simple method to impress an arbitrary amplitude and phase distribution onto an optical wave. The approach uses a ferroelectric liquid crystal spatial light modulator. Aberrations present in the optical system are measured and compensated before the system is used to tune the pupil function of a confocal microscope in a variety of ways.
About the delay in the visual pathway
Author(s):
Jose F. Barraza;
Andrew M. Derrington
Show Abstract
Human observers were required to report whether a briefly- presented static grating appeared ahead of or behind a moving grating, while they fixated on a small marker in between the two gratings. A forced choice paradigm using the method of constant stimuli was adopted to measure the angle of phase corresponding to a perceptual alignment between the two gratings. The angle does not depend on spatial frequency and varies linearly with the temporal frequency. When the experiment was carried out tracking the moving grating, no misalignment between two gratings was found.
Evaluation of transient glare in the scotopic-mesopic range
Author(s):
Elisa M. Colombo;
Jose F. Barraza;
Luis Issolio
Show Abstract
This paper proposes a quantitative method for evaluation of disability glare, considering a scotopic-mesopic range and transient glare. Subjects had to compare brightness of two uniform luminance fields sequentially displayed, one of which was presented under glare conditions. The observer reported which field was brighter with respect to one another. A forced choice paradigm using the method of constant stimuli was adopted to determine the luminance corresponding to the perceptual matching luminance. The results show a non linear effect of the glare illuminance on the matching luminance and a non significant dependence with the luminance reference. We propose an empirical equation to calculate the glare effect. Scattered light can explain the results considering simultaneous contrast.
Performance of the human eye as a wide-angle optical system
Author(s):
Rafael Fonolla Navarro
Show Abstract
This communication reviews some classic and recent studies of the optical performance of the human eye across visual field. Although the retinal image can not be recorded directly, different objective methods have been developed, which permit to determine optical quality parameters, such as the Point Spread Function, the Modulation Transfer Function, the geometrical ray aberrations or the wavefront distortions, in the living human eye. Experimental data obtained with these methods, along with a more exact knowledge of the anatomy (asphericities) of the optical surfaces of the eye, permit us to build more accurate models of the optical system of the eye, learn about its wide-angle optical design, and develop applications.
Improved accuracy tristimulus colorimeters calibrated with standard detectors
Author(s):
George P. Eppeldauer
Show Abstract
A new method has been developed to calibrate tristimulus colorimeters for high accuracy color measurements. Instead of traditional lamp standards, modern, high accuracy detector standards are suggested for calibration. After high accuracy absolute spectral response determination of the tristimulus receivers, color (spectral) correction and peak (amplitude) normalization can minimize uncertainties caused by imperfect realizations of the Commission Internationale de l'Eclairage color matching functions. As a result of the corrections, stable light sources of different spectral power distributions can be measured with an accuracy dominated by the sub 0.1% uncertainty of novel spectral response determinations.
Autofluorescence of ocular tissues: a promising diagnostic technique in ophthalmology
Author(s):
Franco Docchio;
Luigi Rovati
Show Abstract
In the past, ocular diagnosis through fluorometric systems has been mainly based onto exogenous agents. Recently, a number of diagnostic techniques has been proposed for diagnosis of ocular pathologies, which are based upon the naturally occurring fluorescent emission of ocular tissues. In this paper, we discuss major advantages and drawbacks of these techniques, focusing in particular our attention on a novel diagnostic technique based onto autofluorescence of corneal tissue.
Phenomenological analysis of analogue associative processors based on thin holograms
Author(s):
Lyudmila M. Serebryakova;
Alexander S. Rubanov
Show Abstract
Phenomenological analysis is made of analogue associative processors based on thin holograms with superimposed registration. Possibilities of realization of functions of associative memory, associative highlighting of common fragments of object scenes, novelty filter and static phase- conjugate mirror are investigated on the basis of utilization of informative properties of a quadratic off- axis hologram, a hologram of mutually conjugated waves and a system, composed of a linear off-axis hologram and a phase- conjugate mirror.
Room-temperature laser oscillation by F2+ color centers in LiF crystal
Author(s):
Taiju Tsuboi
Show Abstract
Color centers are lattice vacancies which are trapping one or more electrons or holes in ionic crystals. Some of them have been known to be high-gain active materials in tunable solid state lasers. However, most color centers (e.g. FA(II) color center in KC1 crystal) give rise to laser oscillation when the laser-active crystals are cooled with liquid nitrogen [1]. For practical use, it is requested to be able to operate the laser at room temperature (RT) because it is easy to adjust the optical alignment and it is unnecessary to maintain the crystals at liquid nitrogen temperature not only during operation but also after operation to avoid the thermal bleaching of the color centers. The RT stable color center lasers have been achieved predominantly using F2, F2, F2 and F3 color centers in LiF[2,3,4]. Although the RT LiF:F2 color center laser oscillation has been studied by several scientists, all the lasing characteristics have not been clarified.
Photothermoplastic-based diffraction gratings: fabrication and replication processes
Author(s):
Igor V. Ciapurin
Show Abstract
Currently a photothermoplastic medium (PTPM) seems to be rather perspective to fabricate relief-phase diffraction gratings (DGs). The use of a two-layer PTPM comprised a photosensitive semiconductor layer and visualizing thermoplastic layer seems to be appropriate' .ThePTPM is characterized by profitable combination of high values of both photosensitivity (up to lO5lO6 cm/J) and resolution (up to 2000 mm1), with a dry developing process which is fast enough (about 1-5 s). The thinner the thermoplastic layer, the higher the resonant frequency of the PTPM and the wider the recording frequency bandwidth are allowing us to realize high-quality recording of DGs. The DGs' fabrication on PTPM seems to have advantages due to the relief-phase nature of recording process, which is rather convenient for replication of DGs2.
Detection and measurement of invisible static and dynamic objects
Author(s):
Vera Moiseevna Ginzburg
Show Abstract
In report, the results of theoretical and experimental research to develop the methods and means for detection, observing and 3D imaging of static and dynamic objects (e.g., mines and living beings) disposed underwater, or inside or behind optically opaque solid media, will be represented15. The methods for underwater detection and measurements are based on optical refraction, diffraction, and the Talbot effects on the water surface disturbed by ultrasound waves reflected or passed by the object The methods for measurement objects, disposed inside or behind optically non-transparent media, are based on the usage ofmicrowave holographic movie camera recording the radiation passed through the object. The method for detection invisible objects by recording the radiation reflected by objects (for instance, ground mines), is considered.
Self-focusing in microemulsions
Author(s):
Luciano Rosario Maria Vicari
Show Abstract
We study the self-focusing of the gaussian beam given by the Te00 mode of an Ar+ laser by a thin film of a water in oil microemulsions. As microemulsion we use WAD (AOT/water/decane). First experimental results are presented here for beam self-focusing in a WAD film above and under the percolation line.
Photorefractive effects in long narrow BSO-crystals with applied electric field
Author(s):
Gregor Cedilnik;
Matthias Esselbach;
Armin Kiessling;
Richard M. Kowarschik;
Ervin Nippolainen;
Alexei A. Kamshilin;
Victor V. Prokofiev
Show Abstract
In a photorefractive Bi12SiO20 crystal with high applied electric AC field of square-wave shape a fast two- wave coupling response (less than 1 second) and a slow hologram readout decay (minutes) was found for a wavelength of 633 nm. This can be explained by electron-hole transport with two trap-levels. An intensity dependence of the slower complementary grating was found. Illuminating with the readout wave without applied electric field leads to a very slow grating decay (many hours).
Model of VCSEL with two transverse modes with transport
Author(s):
M. S. Torre;
Hector F. Ranea-Sandoval
Show Abstract
We present numerical results from a model of a VCSEL operating in two modes, including the diffusion of carriers. The main conclusion is that the small-signal Modulation Response Function presents peaks corresponding to the resonances of the modes. This function display a more or less pronounced interference if the modes are competing for the same carrier reservoir for which the size of the device is fundamental to determine the overlap between the modal distribution of the field and the carrier distribution into the active region. Results including also transport and capture are similar. Typical evolution of the photon output of both modes displays typical competence traces.
Optical performance of infrared detector with microlens array
Author(s):
Chunlei Du;
Xiangdi Lin;
Lishu Zhou;
Linbo Bai;
Chuankai Qiu
Show Abstract
A new type of diffractive microlens array concentrator has been designed and fabricated for improving the performance of infrared detector array. An experiment was made by coupling the concentrator into a focal plane detector array, the detectivity of the coupled device was increased to nearly 2.8 fold.
Interatomic force constant of AII BIV C2V and AI BIII C2VI optoelectronic materials
Author(s):
Virendra Kumar;
Dinesh Chandra
Show Abstract
Interatomic force constant ((alpha) ) of the A-C and B-C bonds in AIIBIVC2V and AIBIIIC2VI groups of optoelectronic materials has been calculated using plasma oscillations theory of solids. A new relation between force constant and plasmon energy has been obtained. The effect of delocalization of noble metal d- electrons has been taken into account while calculating the force constant of the A-C bond in AIBIIIC2VI semiconductors. On the basis of the best-fit data, another simple equation has been proposed for the calculation of the force constant from their plasmon energy. The calculated values of force constant from these equations have been compared with the values reported by different workers. An excellent agreement has been obtained between them.
Photonics for nuclear industry: issues, problems, and potential solutions
Author(s):
Francis Berghmans;
Andrei I. Gusarov;
Benoit Brichard;
Marc C. Decreton;
Olivier Deparis;
Patrice Megret;
Michel Blondel;
Irina P. Veretennicoff;
Hugo Thienpont
Show Abstract
Nuclear industry shows an increasing interest in the possibilities offered by optical fiber technology. The radiation hardness of many fiber-optic devices still needs to be assessed if optical fiber telecommunication and sensing systems have to be deployed in nuclear facilities. In this paper, we report on recent gamma irradiation experiments on modern fiber optic devices such as special optical fibers, fiber temperature sensors, Bragg gratings and VCSELs. The results indicate that these components can be applied in ionizing radiation environments, even at very high levels of exposure.
Nonclassical effects in nondegenerate optical parametric symmetric coupler
Author(s):
Mohamed Sebawe Abdalla;
Faisal A. A. El-Orany;
Jan Perina Jr.
Show Abstract
In the framework of Hamiltonian formalism nonclassical effects of an optical field propagating inside a directional coupler containing nondegenerate parametric amplification have been studied. We investigate the effect of switching between the input modes and the out going fields from the coupler. Particular attention has been paid to two mode squeezing, second-order correlation function, quasiprobability distribution functions, and photon-number distribution. Incident number and coherent states are considered. It has been shown that when one of the modes enters the coupler in the Fock state and the other modes are in vacuum states, the coupler can serve as a generator for coherent state. Furthermore, regimes for generation and transmission of squeezed and/or sub-Poissonian light are found.
Pulse width tuning by deflector system
Author(s):
Gangyao Xiao;
Shaohe Chen;
Shi Zhong Xu;
Fengqiao Liu;
Lanrong Chen;
Xiaping Ge;
Dianyuan Fan;
Shiji Wang;
Edward S. Fry;
Thomas Walther
Show Abstract
An electro-optic deflector system is developed to re-shape the optical pulse from a Q-switched Nd:YLF oscillator. The shaped optical pulses are tunable in pulse width by scanning the slit and optical pulses of sub 500 ps are obtained. Except the slit width, its position on the scanning plane also determines the shaped pulse width and even causes pulse distortion if the slit is located close to the edge of the scanned beam. The shortest pulse width can be achieved by this system is determined by the transform limitation. This electro-optic deflector system is successfully used in the SG-II high power laser facility.
Spectral properties of hybrid Fabry-Perot resonators with zero-optical path
Author(s):
Yuri P. Udoev
Show Abstract
Spectral dependence of diffraction efficiency is discussed for volume phase reflection gratings with reflective rare boundary. Increasing reflectance at this boundary is shown can result in decreasing Bragg spectral selectivity as well as in arising more sharp resonant effect within central Bragg peak. Effects revealed are interpreted on the base of model of hybrid Fabry-Perot resonator in which internal optical path is equal to zero.
Simultaneous calibration algorithm of phase-shifting based on FFT
Author(s):
Wansong Li;
Likun Su;
Xianyu Su;
Liqun Xiang
Show Abstract
In phase-measuring profilometry, the accuracy of the phase- shifting is very important. In this paper, a new simultaneous calibration algorithm of phase-shifting based on fast Fourier transform (FFT) is presented. The current phase shifting is calculated with the help of the information of an additional fringe pattern and a FFT modulation mask. With this algorithm, we can accurately control the moving of the project grating simultaneous, the accuracy and the automation of the measuring system are improved greatly.
Phase-shift error calibration in modulation measurement profilometry
Author(s):
Likun Su;
Wansong Li;
Xianyu Su;
Liqun Xiang
Show Abstract
Modulation value play a significant role in Modulation Measurement Profilometry. By projection sinusoidal fringe on an object, then shift the sinusoidal grating in one period L(L >= 3) times with equal interval, we can calculate the modulation distribution on the object with these L frames of the fringe pattern. Incorrect modulation can arise when phase-shift error exist. In this paper we give out the general expression of modulation calculation for any phase- shift interval with least-square method when L equals 5. The result proved that the calibration is necessary and useful when phase-shift error exist.
Photorefractive holographic polarization fringe discrimination
Author(s):
Paulo Acioly M. dos Santos;
L. C. da Silva Nunes
Show Abstract
In this work we show a real time holographic polarization fringes discrimination. It is based on the dynamic anisotropic diffraction properties that happen in cubic photorefractive crystals of the sillenite family.
Optical plastic refractive index measurements for NIR region
Author(s):
Ivan D. Nikolov;
Christo D. Ivanov
Show Abstract
Optical plastic materials are widely used in VIS and NIR spectral regions. Plastic components are applied in different devices and especially for NV goggles. A number of plastics have been analyzed as PMMA, PS, PC, and CTE. The refractive indices are computed and measured for these optical plastics. The results obtained are presented and discussed.
Partially coherent effects in Young-Michelson's interferograms
Author(s):
Roman Castaneda;
Francisco F. Medina-Estrada;
Mario Garavaglia;
Lia Maria Zerbino
Show Abstract
Young's interferograms with high visibility reveals a high degree of spatial coherence. However, effects due spatially partial coherence can be observed when a Young's interference pattern interferes itself through a compensated Michelson's interferometer, which is attached at the exit of the Young's slit pair, as we show in this paper.
New method for analysis of optical planar gradient waveguides
Author(s):
Nikolai D. Espinosa Ortiz
Show Abstract
This method is designed to analyze the propagation constants, critical frequencies and the electromagnetic field on the planar optical waveguide with arbitrary distribution of dielectric constant profile (epsilon) (y). Also, this method allow us the recuperation of the distribution of profile (epsilon) (y) with the propagation's constants obtained from experimental data.
Fresnel diffraction from a step in reflection and transmission modes
Author(s):
Mohammad Taghi Tavassoly;
M. Sahlol-Bai;
M. Salehi;
Hamid Reza Khalesifard
Show Abstract
Fresnel diffraction from a step, in reflection and transmission modes is studied. The study shows that the resulting diffraction pattern is similar to that of a semi- infinite obstacle, but the intensity distribution near the step edge is very sensitive to the step height and is a periodic function of the height. Therefore the effect can be exploited for measuring the heights and optical path differences of the coated films, strips, and small displacements.
Wavelength-compensated broadband Fourier transformer
Author(s):
G. Minguez-Vega;
Jesus Saez Lancis;
Enrique Tajahuerce;
Mercedes Fernandez-Alonso;
Vicent Climent;
Pedro Andres
Show Abstract
We report herein an hybrid (diffractive-refractive) lens triplet showing quasi-wavelength-independent optical Fourier transform capabilities. The wavelength compensation carried out by our novel optical design is exact for the axial position of the Fourier transform of the input. Nevertheless, a very low residual transversal chromatic aberration remains. Results of laboratory experiments will be shown.
Diffractive near-field array generators
Author(s):
Werner Klaus;
Ayako Okazaki;
Haruka Suzuki;
Tomoko Nakayama;
Kashiko Kodate
Show Abstract
In this paper, we compare and summarize the features of two types of 2D array illuminators--the binary zone plate array and the Talbot array illuminator--both producing a spot array in the near field without the addition of any optical component. Numerical evaluations of the illumination efficiency are based on the scalar theory. We present and discuss furthermore the experimental results obtained by such array illuminators when fabricated under the same conditions, i.e., by optical lithography and two masks (four-level binary optics).
Nonlinear thin-layer theory and approximative techniques
Author(s):
Timo A. Laine;
Ari T. Friberg
Show Abstract
We derive a thin-layer theory for stratified nonlinear structures. By using a superposition of plane waves we solve the Kerr-Maxwell equation rigorously within a thin slab. We construct the characteristic matrix of the medium and show that the wave vectors become field dependent. We also consider alternative methods that can be employed in layered nonlinear structures. Especially we make use of the calculus of variations and Hamilton's canonical perturbation theory.
Real-time interferometric measurement of differential refractive index in low-concentration solutions
Author(s):
Jose E. Calatroni;
Carmen Sainz;
Antonio L. Guerrero;
Rafael A. Escalona Z.
Show Abstract
Spectrally Resolved White Light Interferometry is used for real-time high-precision measurement of differential refractive index of low concentration solutions. Dispersion behavior of low concentration solutions is similar to that of their solvents, so that the differential refractive index is non-dispersive. White light provides redundant information which yields high precision results. Moreover, white light provides information about the absolute fringes' order, which allows to improve precision.
Development of a new particle counter for simultaneous measurement of the size distribution, concentration, and estimation of the shape factor of liquidborne particles
Author(s):
Aladar Czitrovszky;
Attila Nagy;
Peter Jani
Show Abstract
A new liquid-borne particle counter is described that utilizes an optimized optical setup to determine the size distribution and concentration by two different methods and to estimate the shape-factor of the suspended particles. The aim of this optimization was to achieve the appropriate optical conditions for such type of measurement, viz. determining the geometry of the illumination and detection, and calculating the testing volume and dependence of the parameters of detected signal on the particle size for pulse height and pulse duration methods performed at the same illumination and detection conditions. The main benefit of the developed device is the high dynamic range of the size determination of the micron-size liquid-borne particles and the possibility of estimating their shape-factor. The proposed measurement method was incorporated in a PC- controlled LQB-1-200-L-T liquid-borne laser particle counter developed on the basis of our previous APC-03-2 and APC-03- 2A air-borne particle counters and a LQB-1-200 liquid-borne particle counter.
Novel approach for exceeding the resolving power of optical systems
Author(s):
Zeev Zalevsky;
David Mendlovic;
Adolf W. Lohmann;
Gal Shabtay
Show Abstract
This project deals with a novel approach for exceeding the resolving power of optical systems. The concept is based on a moving pre-designed, pseudo random, quasi-periodic grating that is located close to the object. The scanning property of the observing CCD camera is used for performing the final high-resolution restoration of the object.
Diffrent spectra in near and far field of dipole
Author(s):
Mufei Xiao
Show Abstract
We demonstrate theoretically that for polychromatic incident light of Gaussian spectrum, a dipole radiates with a redshifted spectrum. The degree of the shift depends on the radiation distance. The shift disappears in far field limit. These spectral changes are not caused by dispersive optical response of the source, nor stemming from correlations in distributions of source or scattering medium. Therefore, the demonstrated spectral changes are due to the nearness of the observation point. In other words, one states that the near field spectra, in general, bear a redshift with respect to the far field spectra.
Design of an optical correlator with totally incoherent light
Author(s):
Avi Pe'er;
Dayong Wang;
Asher A. Friesem;
Adolf W. Lohmann
Show Abstract
An optical spatial filtering system, designed to operate with totally incoherent light sources is presented. When correlating with such polychromatic light sources, one major problem is the dependence of the correlation response scaling on wavelength. A theoretical system that exactly compensate for this problem is analyzed. A practical configuration for implementing such a system, satisfying the theoretical solution up to first order in wavelength, is proposed. This configuration includes a combination of diffractive and refractive lenses and a gray scale filter. The possibility of higher order approximations is considered.
Use of optical methods for studying the influence of laser radiation on human organism
Author(s):
Alexander N. Korolevich;
Natali P. Prigun
Show Abstract
While low-intensity laser radiation is widely used for the medical treatment of various illnesses, its effective mechanism on human organism are far from being completely investigated. He-Ne laser effects on aggregation characteristics of donor's whole blood were studied for heart ischemia sicks. We monitored biochemical characteristics by standard clinical methods. The oxygenation degree of blood and changes in erythrocytes aggregation sizes under normal and pathological states have been monitored independently by optical means. One of possible mechanism of laser influence under laser therapy was found.
Intramolecular coupling effects on the four-wave mixing signal
Author(s):
Teresa Cusati;
J. L. Paz;
M. C. Salazar;
A. J. Hernandez
Show Abstract
In this work we have studied the effect of the intramolecular coupling on the spectral properties of an ensemble of two-level systems carrying homogeneously distributed resonance frequencies, considering permanent dipole moments non zero for a Malachite Green solution.
Straightness measurements using a reflection confocal optical system
Author(s):
Kiyofumi Matsuda;
Tomoaki Eiju;
Maitreyee Roy;
John W. O'Byrne;
Pal W. Fekete;
Colin J. R. Sheppard
Show Abstract
Straightness measurement is a very important technique in the field of mechanical engineering. A particular application would be very high accuracy machining on a diamond turning lathe. In this paper a novel optical method for measuring straightness of motion using reflection confocal optics is proposed. The advantage of this method in comparison with the transmission optical systems used by Burch and Williams is that the lateral displacements in the direction of the two axes perpendicular to the optical axis, and the rotation angles around all three axes, can be measured simultaneously. This can be very useful for straightness measurement. Also, reflection optical systems are more compact in length.
Scattering of light by identical cavities ruled on a highly conducting surface
Author(s):
Diana C. Skigin;
Ricardo A. Depine
Show Abstract
We study the scattering of light from almost closed cylindrical cavities ruled on a highly conducting flat surface. We consider the case where the shape of each cavity can be described by an arbitrary multivalued function of the coordinates. By using the multilayer modal method, which combines the multilayer approximation with the R-matrix propagation algorithm, we investigate the electromagnetic response of this kind of scatterer when it is illuminated by s or p polarized plane waves. Our results show that for both polarizations this system exhibits a resonant behavior manifested by sharp variations in the curves of scattered intensity versus wavelength which are associated with strong intensifications of the near field. The wavelengths at which the resonance occur are intimately connected with the eigenmodes of a single cavity.
Birefringent properties of (MgGeF6) 6H2O Crystals
Author(s):
Sergiy Sveleba;
Volodymyr S. Zhmurko;
Volodymyr Kapustianik;
Yuriy Pankivskyi;
Ryszard Hrabanski
Show Abstract
The temperature dependences of the optical birefringence (delta) ((Delta) n) in (MgGeF6)(DOT)6H2O crystals have been investigated. Observed specific properties such as global hysteresis, kinetic effect, thermooptic memory effect, localization of the incommensurability wave vector on the commensurate values of higher order, sensibility to the external mechanical stress confirm existence of the incommensurate phase in (MgGeF6)(DOT)6H2O crystals.
Magnetization-induced second-harmonic generation imaging of buried magnetic interfaces
Author(s):
Gilles Tessier;
Patrick M. Georges;
Alain Brun;
Peter Meyer;
Jacques Ferre;
P. Beauvillain;
V. Mathet
Show Abstract
Magnetization-induced second harmonic generation is selectively sensitive to the magnetization of surfaces or buried interfaces. We have used it to obtain images covering areas up to 100 micrometers wide of the magnetic domain structures of Fe/Pd and Co/Pt buried interfaces with a micrometer resolution.
Retrace error for the measurement of a long-radius optic
Author(s):
Sen Han;
Erik Novak
Show Abstract
The error caused by nonzero fringe pattern in a phase shifting interferometer is `harmful' to testing a long radius optic. In this paper, with the help of a concept of retrace error the error is analyzed through the combination of experiments with simulated calculations, and more sensitive elements are found in system alignment, so that the effect of the misalignment of optical elements on the retrace error is reduced to minimum.
Investigations on the frequency measuring error of laser Doppler velocimeters using the quadrature demodulation technique
Author(s):
Juergen W. Czarske;
O. Doelle
Show Abstract
We present the application of the quadrature demodulation technique (QDT) for time-resolved frequency measurements in laser Doppler velocimetry (LDV). In contrast to conventional frequency estimators like FFT, the QDT allows the determination of the Doppler frequency nearly independent of the number of the occurring signal periods, so that a high time resolution can be achieved. The resulting frequency error of the QDT is investigated in dependence on relevant LDV signal parameters like SNR and time duration. Furthermore, the optimum averaging time for the processing of gaussian burst signals was determined. The minimum frequency uncertainty of the QDT occurs for an averaging time of the approximately equals 1/e burst duration at the thermal noise, and the approximately equals 1/e2 burst duration at shot noise, respectively.
Anomalous scaling properties of optical excitations in random media
Author(s):
Alexander L. Burin;
Mark A. Ratner
Show Abstract
The eigenstates of small radius molecular excitations, coupled by the resonant dipole-dipole interaction, are examined for a system of random resonant centers. Anomalous scaling properties are seen even in the absence of external disordering, i.e. their properties are intermediate between localized and `true' delocalized states. The effective transport properties of excitations can be described in terms of anomalous diffusion, with a distance dependent diffusion coefficient scaling as D approximately 1/R. This anomalous behavior agrees with our simulation of boundary quenching of excitons and with the related experiment on organic light emitting diodes.
Thermal-lens measurements of fluorescence quantum efficiency in Nd+3-doped fluoride glasses
Author(s):
S. M. Lima;
Tomaz Catunda;
R. Lebullenger;
Antonio Carlos Hernandes;
Mauro L. Baesso;
A. C. Bento
Show Abstract
We measured the quantum efficiency ((eta) ) in the concentration range 0.5 - 3.6% Nd+3 doped ZBLAN using a Thermal Lens method. At room temperature and 1 mol% Nd+3 we obtained (eta) equals 0.88 in good agreement with previous Judd-Ofelt calculations.
Z-scan measurements in saturable nonlinear refraction media
Author(s):
E. Tenorio;
Tomaz Catunda
Show Abstract
The well-known Z-scan tecimique has been extensively applied to the study of large class of nonlinear materials. In some cases, particularly in optical limiters applications, it is important to study the nonlinearity in the high intensity regime where most material's nonlinear properties saturate with the light intensity. This saturation effect causes a change in the nonsaturated gaussian refractive index profile and consequently the usual Z-scan theory can not be used. We have studied this problem calculating the far-field pattern of the beam, transmitted by a nonlinear material, using the Kirchhoff-Fraunhofer diffraction integral. We also performed Zscan experiments in chromium doped saturable absorbers ruby, alexandrite and GdAlO3:Cr3. We believe that these materials are very suitable to this study because they present high saturable nonlinear refractive index, the experiments can be made with Ar laser in the cw regime and their properties are very well characterized in previous works'.
Apodizing filters for imaging through highly scattering media
Author(s):
Manjula D. Sharma;
Colin J. R. Sheppard
Show Abstract
Confocal microscopy can be used to image through a highly scattering medium, the optical sectioning property rejecting light scattered from regions other than the focal plane. Apodizing filters designed to improve this rejection at the expense of some degradation in axial resolution are considered.
Testing of cylindrical lenses by grazing incidence interferometry
Author(s):
Hans Nuerge;
Johannes Schwider
Show Abstract
In order to measure geometrical errors of the fabrication process of cylindrical lenses, a grazing incidence interferometer is used to test 4 surfaces of the lenses. Two specially designed diffractive optical elements are working as beam splitter, recombiner as well as reference for the ideal lens shape and ideal centration of the surfaces relative to each other.
Enlarging viewing angle of computer-generated holograms
Author(s):
Hiroshi Yoshikawa;
Mikio Yamagishi
Show Abstract
We investigate the use of lens-less Fourier hologram to enlarge viewing angle of the computer-generated holograms (CGH) whose resolution is relatively low such as a photographic reduction. For image reconstruction, this hologram requires the point illumination source near the hologram. To avoid the use of such special illumination, we made secondary hologram with collimated reference beam and the reconstructed beam of the CGH. The second hologram has wide viewing angle and can be reconstructed with collimated white-light illumination.
Squeezing in detuned second-harmonic generation
Author(s):
M. K. Olsen;
S. C.G. Granja;
R. J. Horowicz
Show Abstract
We investigate the effects of cavity detuning on the rotation and displacement of the uncertainty ellipse in cavity second harmonic generation. This is of topical interest due to recent work on quantum tomography, which allows experimental measurement of the Wigner function for light fields. We also investigate to what extent the decrease in quadrature squeezing with detuning can be attributed solely to the resulting depletion of the intra- cavity fields.
Hidden phase effects in estimating the minimum-variance pupil plane field of a coherently illuminated far-field object
Author(s):
William W. Arrasmith
Show Abstract
Recently, it has been shown that least squares phase estimators require the determination of a hidden phase to properly reconstruct a field that contains branch points. The branch points, resulting from zeros in the complex field, occur at random locations. These branch points introduce discontinuities in the 2D phase function that have a magnitude of 2(pi) . Conventional least squares and minimum variance phase reconstructors do not properly sense these discontinuities and therefore have difficulty in reconstructing the field resulting from a coherently illuminated object. Preliminary investigations are made in determining the utility of the hidden phase to the minimum variance based phase reconstructors. A simple 2D image model is reconstructed using the hidden phase adjustments.
Anthropomorphic OPR method
Author(s):
Vera Moiseevna Ginzburg
Show Abstract
Problem of optical pattern recognition (OPR) is sorting numerous images into several subsets. A certain generalized image is ascribed to each subject. For example, the letter "A", written in different fonts, to some generalized image of this letter. In this process one has to deprive it of individual attributes i.e. to narrow down its spatial spectrum. This results to a generalized object's image with informative fragments (IF) at places with sharp form typical to many similar images. From Optics it is known, ' 2 the defocusing of an image in non-coherent light using a lens (camera) cuts off high-frequency components of the spatial frequency spectrum transmitted by the optical system and therefore removes the small details of the image. It is shown that in Nature such process can be realized by existing periodic defocusing of the crystalline lens3, which leads to generalization of an image projected on the retina. It is shown that image defocusing can be used in technique for generalization real images in OPR systems. It was proposed the scheme of possible variant of such robot "drawing" the generalized images of real objects. This scheme represents a holographic correlator processing images by defocusing and by applying a set of spatial filters. These filters are constructed using a set of elementary images ("geometrical alphabet") formed from two images, a straight stripe and round spot, recognized by all living beings4. The results of computer imitation of "drawing" generalized images by such robot, are presented. Fig.! demonstrates some examples of contour images and their defocusing images with informative fragments
Thermo-optical coefficients of some crystals containing Li and B ions
Author(s):
Ivetta T. Bodnar
Show Abstract
Refractive indices of some transparent crystals containing Li and B ions were measured in wide temperature range. They are ferroelectrics LiNbO3 and LiTaO3, laser crystals BaB2O4 and LiB3O5, and lithium tetraborate. The refractive indices were measured by the least deviation method on goniometer-spectrometer with 1.5 (DOT) 10-4 precision. Thermooptical coefficients were calculated on the basis of experimentally obtained temperature values of the refractive indices. A comparative analysis of temperature behavior of the refractive indices and the thermooptical coefficients for relative crystals of lithium niobate and lithium tantalate and also barium (beta) -borate and lithium triborate was carried out.
Suitability of fractional moments for data from low-dynamics acquisition systems
Author(s):
Claudia Innocenti;
Anna Consortini
Show Abstract
The distributions of intensity fluctuations generally found in atmospheric optical scintillation measurements are characterized by a large range of intensity values, I, whose probability level, even if low, is not negligible. The range of I-values with a significant probability depends on the experimental conditions and can go from zero to several hundred times the mean value, < I <, of the distribution in the case of strong scintillation. In principle, an acquisition system should have dynamics able to cover the whole significant range of measured intensities. Of course, this requirement is not limited to scintillation measurements and the application of low order fractional moments we present here can be employed every time we face a measured quantity with a "long tail" distribution.
Optical simulations of skin diagnosis with account of multiple surface scattering events
Author(s):
Ervin Goldfain
Show Abstract
To fully exploit current optical methods of skin diagnosis, it is desirable to understand the physics underlying photon migration in epithelial tissue. A number of approaches have been developed to meet this challenge. Most simulations are based upon the radiative transport theory which describes the sequential transfer of diffuse light through the stack of skin layers. These models are computationally intensive and typically rely upon the following assumptions: (1) volume scattering of photons inside the collagen fiber layer is predominant, (2) photons undergo Fresnel reflections on each boundary, (3) scattering can be modeled along each path using prescribed phase functions such as Henyey-Greenstein or Mie. Our work simulates photon migration in skin from a different standpoint: using a commercially available optics code, we randomly trace a large number of photons and assign generic absorption and scattering properties to all boundaries, including the ones separating sublayers of collagen fibers. As a result, single and multiple surface scattering events are account for. Absorbing inhomogeneities may be included as light obstructions and fluorophores as secondary sources, respectively. This preliminary work is targeted for clinical applications involving skin imaging and spectroscopy.
High-intensity effects in liquid crystals driven by 532-nm nanosecond laser pulses
Author(s):
Svetlana G. Lukishova
Show Abstract
We observed unusual high-contrast, far-field, elliptical diffraction rings in a green, linear polarized nanosecond laser beam, a phenomenon strongly dependent on the orientation of the nematic liquid crystal molecules, under the experimental conditions excluding ordinary orientational or thermal self-focusing. The threshold of the nonlinearity is modified either by changing the laser repetition rate (cumulative nature) or by adding a two-photon absorbing chromophore.
Design and replication of diffractive optics for smart pixel applications
Author(s):
Richard V. Stone;
Jack Ko;
Peter S. Guilfoyle;
John M. Hessenbruch
Show Abstract
High quality diffractive optical interconnect elements (DOIEs) were designed and fabricated for integration into a smart pixel, high performance optoelectronic computing module system. A cost effective DOIE replication method was developed in which the fine features of a candidate set of DOIEs were successfully reproduced. Accurate multiple phase levels were replicated utilizing an injection molding technique. This process was developed using two different types of materials: a copolymer and an acrylic. One hundred units were successfully reproduced (50 units of the copolymer and 50 units of the acrylic) from a single master DOIE that contained 2 micrometers X 2 micrometers pixels with up to 64 phase levels per pixel.
Light scattering of finite beams in stochastic media
Author(s):
Jostein Herredsvela;
Jakob J. Stamnes;
Knut H. Stamnes
Show Abstract
By using a new method of solving the radiative transfer equation, we calculate the diffuse (i.e. scattered) radiance due to a Gaussian beam incident on a slab of finite thickness filled with scattering particles. The radiance is calculated for several observation angles and at any point inside or at the boundaries of the slab, both for isotropically and weakly anisotropically scattering media.
Intensity fluctuation in ring lasers due to the back scattering from outside mirrors
Author(s):
Jung-Young Son;
Yong-Jin Choi;
I. A. Strilets
Show Abstract
The intensity difference between counter propagating waves in ring lasers when back scattering is provides by the outside mirrors is analyzed. The difference can be expressed as a function of the distances between two ring laser mirrors and their corresponding mirrors when the ring laser is operating in locking zone regime. This difference can be applied to measure a displacement with sub-nanometer accuracy.
Characterization of atmospheric turbulence by means of thin beams
Author(s):
Anna Consortini;
G. Paoli;
Florence Rigal;
Claudia Innocenti;
Yi Yi Sun
Show Abstract
In atmospheric and astronomical optics, as well as in applications involving optical propagation through the atmosphere, atmospheric turbulence plays an important role in deterioration of information. Recently, adaptive systems allow correction of aberrations produced by turbulence. In all cases knowledge is necessary of atmospheric turbulence and its characteristic parameters, i.e. inner scale, outer scale and the so called structure constant.
Fiber optics chemical sensor FOCA 2000
Author(s):
Robert J. Brunner;
Juraj Doupovec;
Frank Kvasnik
Show Abstract
A modular fiberoptic sensorial instrument for (bio-)chemical analyses will be presented. The sensing mechanism is based on Capillary Optical Fiber (COF). A measurand of liquids or gaseous form present in the COF cavity influences the chemical transducer covering the inner wall of fiber, and by this way changes the intensity of guided radiation. The wavelength scanning through the characteristic region enables the identification and quantitative analysis of the measurand. Every COF modulus is sesibilized for specific chemicals. The application of new immobilized chemical transducer and theoretical description of the sensing effects will be presented, too.
Precision length change followed by dynamic detection of the laser frequency locked to interference fringe
Author(s):
Seiichi Kakuma;
Jun Hoshii;
Norihiko Takahashi;
Ryoji Ohba
Show Abstract
This paper describes a new interferometric method to measure length changes precisely. Frequency of a laser which is locked to one of interference fringe intensity peaks of an interferometer so that it may change linearly proportional to displacement given to one of the interferometer mirrors. The frequency shift is determined by direct beam frequency counting referring another frequency stabilized laser. Resolution of nm is achieved.
Diffraction, relativity, and quantum mechanics
Author(s):
Henri H. Arsenault
Show Abstract
At the recent conference on Optics in Education in Deift, I presented a paper' where I claimed that a new formulation of scalar diffraction based on an angular representation was simpler, more accurate and easier to teach than the classical manner based on various approximations of the spatial distribution. To my surprise, the presentation generated a storm of protest by some participants in the congress, who claimed that my results were wrong and my derivation invalid. Although my results were not wrong, it is true that the demonstrations were more intuitive than rigorous. Since that time, I have reexamined my results and found that I can put them in a rigorous form by means of some relatively elementary quantum and relativistic properties of light
Imaging properties of the Gabor super-lens
Author(s):
Christian Hembd-Soellner;
Richard F. Stevens;
Michael C. Hutley
Show Abstract
In 1940 Gabor described an optical system consisting of a pair of arrays of microlenses. The arrays were separated by the sum of their focal lengths and there was a small difference between the periods of the two arrays. The overall effect was to perform a function similar to that of a lens with dimensions much larger than the microlenses in the arrays. Images formed by this system exhibit unusual properties and appear not to obey the normal rules of optics, for example, the magnification is not necessarily equal to the ratio of image to object distances. Gabor assigned the term `superlens' to the system.
Light scattering from a bilayer system
Author(s):
Raul Garcia-Llamas;
Luis Efrain Regalado;
Claude Amra
Show Abstract
The scattered light from a bi-layer system with a shallow random rough surface bounded by semi-infinite dissimilar optical media is calculated. Results are obtained by assuming a gaussian roughness spectrum for the random rough surface and the formalism is applied to simulate the scattering in the ATR-Kretschmann configuration, allowing the excitation of guided waves.
Detection of virus in shrimp using digital color correlation
Author(s):
Josue Alvarez-Borrego;
Cristina Chavez-Sanchez;
Mario Alonso Bueno-Ibarra
Show Abstract
Detection of virus in shrimp tissue using digital color correlation is presented. Phase filters in three channels (red, green and blue) were used in order to detect HPV virus like target. These first results obtained showed that is possible to detect virus in shrimp tissue. More research must be made with color correlation in order to consider natural morphology of the virus, color, scale and rotation and noise in the samples.
SRS line narrowing and optical induced birefringence in dye-doped CS2
Author(s):
Ricardo Rego Bordalo Correia;
Petrus A. Alcantara Jr.;
Silvio L. S. Cunha
Show Abstract
It has been observed the effect of the addition of small concentrations of an absorbing dye (approximately 10 ppm of Coumarin 337) on the super-broadening process of CS2 stimulated scattering lines in a capillary fiber. This effect is attributed to the selective absorption of dye molecules, which creates an anisotropic distribution of these molecules in the excited- and ground states, which possess different static dipole moments. This asymmetry affects the orientation of the CS2 molecules through the modification of the local field, as measured by changing the spectral distribution of stimulated scattering and the optical induced birefringence of the liquid.
Moire in interference with spatial coherence beams
Author(s):
Roman Castaneda;
Francisco F. Medina-Estrada
Show Abstract
In this paper we study the propagation of coherence beams from a non-regular 1D grating to an observation plane in the Fraunhofer domain. The cross-spectral densities at both the grating and the observation plane are analyzed. The concept of spatial coherence Moire was introduced to analyze the cross-spectral density at the observation plane of the corresponding interference field.
Use of entangled-photon imaging in optical biopsy: a feasibility study
Author(s):
Ervin Goldfain
Show Abstract
We examine a novel diagnostic method suitable for optical biopsy, i.e., the noninvasive in vivo detection of malignant lesions in human tissue. Entangled-photon imaging is an emerging technology based upon the use of non-classical sources of light such as optical parametric oscillators (OPO). These sources generate above-threshold signal and idler beams that have intensity fluctuations highly correlated in space and time (twin beams). It has been shown that low-intensity OPO's make possible high sensitivity absorption measurements of weak targets, below the shot- noise limit. The direct use of this technology for optical biopsy is severely restricted by the large amount of scattering noise associated with light-tissue interaction. We report what is, to our knowledge, the first feasibility study on a differential wavelength, OPO-based setup targeted for mammography. Constraints related to the entanglement time, OPO selection and background suppression are analyzed. The paper concludes with a review of future developments and challenges.
Reflective nonlinearities in high-power chiral liquid crystal laser optics
Author(s):
Svetlana G. Lukishova;
Konstantin S. Lebedev;
Ekaterina A. Magulariya;
Sergey V. Belyaev;
Nicolay V. Malimonenko;
Ansgar W. Schmid
Show Abstract
High-intensity circular polarized light beams tuned to selective-reflection condition in ultra-pure cholesteric liquid-crystal layer made possible observation of athermal light-induced drop in the chiral reflection coefficient of liquid-crystal layer. The dependence of the effect on intensity (not on average power) permits one to connect it mechanistically with the chiral CLC helix pitch dilation up to spiral untwisting. Under the current, specifically chosen experimental irradiation conditions, nonlinear bleaching of the medium's reflectivity could be observed over time intervals that allow a distinction in the driving mechanism of nonlinear bleaching between optical-field-induced and thermal effects. The effect was observed both in free space and inside laser resonator, where CLC layer was used as end mirror.
Hierarchical fuzzy optical syntactic pattern recognition
Author(s):
H. John Caulfield
Show Abstract
In previous work, my students and I have shown that optical fuzzy syntactic pattern recognition was far more robust than prior optical pattern recognition methods. Here, I add methods which allow context to influence the decision as to what object is present. The letter is in the context of a word which is in the context of a sentence which... . General optical systems for this are described.
Influence of objects buried in highly dense media on angular correlations of the scattered intensity
Author(s):
Suguru Sangu;
Takashi Okamoto;
Jun Uozumi;
Toshimitsu Asakura
Show Abstract
We sometimes want to know some information hidden in highly dense media in which the light suffers a strongly multiple scattering, such as the existence of a tumor in a biological tissue and a state of a material behind a layer of paint. In such situations, optical measurement techniques which have the advantage of a non-contact and non-invasive method have been remarked and studied actively by many scientists.1 In the present paper, we pay attention to speckle-like intensity fluctuations generated by multiply scattered light and to their angular correlation properties, and investigate an effect of objects buried in highly dense media on an angular correlation function of the scattered intensity. The angular correlation function is derived theoretically and numerical simulation results are shown.
Spectroscopic polarimeter based on optical frequency-domain interferometry
Author(s):
Kazuhiko Oka;
Takayuki Kato
Show Abstract
This paper presents a novel method for the spectroscopic measurement of the state of polarization of light. A pair of thick retarders made of quartz are incorporated into the polarimeter to obtain a broadband spectrum including three quasi-sinusoidal components. This spectrum offers the significant information to determine the frequency-dependent Stokes parameters of the light under measurement. Unlike the conventional polarimeters, no mechanical movable component for polarization alignment is required.
Simulated quenching with temperature rescaling for designing diffractive optical elements
Author(s):
Jean-Numa Gillet;
Yunlong Sheng
Show Abstract
We propose a novel algorithm for designing diffractive optical elements, which uses the concept of adaptive simulated annealing and ensemble simulated annealing. We iteratively rescale the temperature in the end of each quenching process, according to the ensemble statistics, to bring the system back from a frozen state to thermodynamical equilibrium for avoiding the local minimum. The process is used to design binary phase irregular spot array generators. The diffractive element has trapezoidal apertures of varying heights that are adapted to the e-beam plotting and provide a large number of degrees of freedom.
Spectroscopic study of neodymium-doped LilnS2 single crystals
Author(s):
Alexander P. Yelisseyev;
Sergei Lobanov;
Ludmila I. Isaenko;
Jean-Jacques Zondy
Show Abstract
Nd-doped LiInS2 single crystals were grown using the Bridgeman technique and their optical properties studied. An intense emission with a dominant line at 1077 nm and groups of lines centered at 600, 760, 820 and 890 nm in absorption/luminescence excitation spectra are related to Nd3+. Doping results in a considerable increase of broad band absorption in the 400 - 460 nm range and a blue emission line at 440 nm at 80 K. Both are associated with transitions between InLi level and valence band.
Analytical description of quasi-orthogonal and random binary optical phase element properties
Author(s):
Mykhajlo V. Shovgenyuk;
Tares Ye Krokhmalskii;
Mykhailo P. Kozlovskii
Show Abstract
Optical properties of binary phase elements (BPE) are described on the basis of the coordinate-frequency signals distribution method. Analytical expressions for the autocorrelation function and the Wiener's spectrum of BPE spatial frequencies are obtained. Based on these expressions, a generalized optical parameter for the numerical evaluation of optical noise level as well as intensity fluctuations of Wiener's spectrum interference pattern are calculated. Statistical phase elements description is proposed as a basis to introduce a non- orthogonality parameter for characteristics of phase binary distribution. A graphic representation of optical parameter vs non-orthogonality parameter relation is proposed for the description of classes of orthogonal, quasiorthogonal and random BPE.
Online fringe tracking and prediction at IOTA
Author(s):
Edward Wilson;
Robert W. Mah
Show Abstract
The Infrared/Optical Telescope Array (IOTA) is a multi- aperture Michelson interferometer located on Mt. Hopkins near Tucson, Arizona. To enable viewing of fainter targets, an on-line fringe tracking system is presently under development at NASA Ames Research Center. The system has been developed off-line using actual data from IOTA, and is presently undergoing on-line implementation at IOTA. The system has two parts: (1) a fringe tracking system that identifies the center of a fringe packet by fitting a parametric model to the data; and (2) a fringe packet motion prediction system that uses characteristics of past fringe packets to predict fringe packet motion. Combined, this information will be used to optimize on-line the scanning trajectory, resulting in improved visibility of faint targets. Fringe packet identification is highly accurate and robust (99% of the 4000 fringe packets were identified correctly, the remaining 1D were either out of the scan range or too noisy to be seen) and is performed in 30 - 90 milliseconds (depending on desired accuracy) on a Pentium II-based computer. Fringe packet prediction, currently performed using an adaptive linear predictor, delivers a 10% improvement over the baseline of predicting no motion.
Directional achromatic laser Doppler anemometer employing powerful diode-pumped fiber lasers
Author(s):
Juergen W. Czarske;
Holger Zellmer;
K. Plamann;
Herbert Welling
Show Abstract
Diode pumped fiber lasers are compact reliable light sources and achieve today over 30 W fundamental mode power. Hence, they are attractive for the realization of portable laser Doppler anemometer (LDA) systems with high optical power. We present the application of fiber lasers together with diffraction optics for the realization of a miniaturized achromatic directional LDA system. Different methods for the realization of the directional discrimination of the scattering particle movement were investigated and compared. (1) The use of Bragg cells as frequency shifter and diffractive beam splitter for the realization of a heterodyne technique. (2) The application of a two- wavelength fiber laser and Fourier optical phase shifters for the realization of a homodyne technique. (3) The detection of the position of the scattering particle in the measuring volume by dual-fiber receiving techniques.
Paper formation analysis using the power spectrum of light transmission images
Author(s):
Mouade Bouydain;
Jose F. Colom;
Rafael Fonolla Navarro;
Josep Mallofre Pladellorens
Show Abstract
The paper formation is one of the most important properties of the paper but remains a difficult property to determine. A method for determining this property has been developed. This method based on light transmission image analysis uses the power spectra of the Fourier transform to analyze the floc distribution. The method has been tested for various furnishes and allows a well discrimination between different qualities of formation that does the standard formation number.
Tolerance in color pattern recognition in the RGB system
Author(s):
Montserrat Corbalan-Fuertes;
Maria Sagrario Millan Garcia-Verela;
Maria Josefa Yzuel
Show Abstract
We propose a method to evaluate the tolerance in color pattern recognition by multichannel correlation in the RGB system. For monocolor objects with equal shape on black background we define a range of recognition in the scene plane. The application of the range of recognition in the three channels gives the tolerance to color variations. As an application we study the tolerance of the recognition system to illuminant changes in the image acquisition. We use common lightings such as fluorescent, incandescent and daylight. The results show that the tolerance decreases for colors with a low contribution in at least one channel.
Fiber optical sensor for the determination of adulteration in petrol
Author(s):
L. M. Bali;
Atul Kumar Srivastava;
Rajesh Kumar Shukla;
Anchal Srivastava
Show Abstract
The newly designed prism based fiber optical refractometer sensor has been used to determine adulteration in petrol. A procedure for identification of the adulterant and determination of its concentration in a sample of petrol has been reported. Substances like kerosene, diesel, a mixture of these two or of aviation gasoline and kerosene have been used as adulterants.
Optical logic-neural field using computer-generated Fresnel holograms
Author(s):
Kunihiko Mori;
Noritake Izaiku;
Kenn Kawaharada;
Takayasu Fuchida;
Sadayuki Murashima
Show Abstract
The logical neuron is defined that its output is decided by own truth table and a combination of input logic. The logical neuron has some different characteristics in comparison with the threshold type neuron. Also, the logicneural field is defined as interconnection of the several logical neurons"2. It is interesting to investigate behavior of the logic-neural field. An optical logic-element using an array of computer-generated Fresnel holograms (Fresnel CGHs) was reported3. In the method, each logical element is driven by two coded input and generates a coded output according to same rule of input. The output of the element can be introduced to input of next elements. Therefor, there is a possibility that the logic-neural field can be realized by the optical logic-element. In this paper, the optical logic-element using an array of Fresnel CGHs is studied for one dimensional optical logic-neural field as shown in Fig. 1
High-reliability GaAs image intensifier with unfilmed microchannel plate
Author(s):
Edward J. Bender;
Joseph P. Estrera;
C. E. Ford;
A. Giordana;
John W. Glesener;
P. P. Lin;
A. J. Nico;
Timothy W. Sinor;
R. H. Smithson
Show Abstract
Current GaAs image intensifier technology requires that the microchannel plate (MCP) have a thin dielectric film on the side facing the photocathode. This protective coating substantially reduces the amount of outgassing of ions and neutral species from the microchannels. The prevention of MCP outgassing is necessary in order to prevent the `poisoning' of the Cs:O surface on the GaAs photocathode. Many authors have experimented with omitting the MCP coating. The results of such experiments invariably lead to an intensifier with a reported useful life of less than 100 hours, due to contamination of the Cs:O layer on the photocathode. Unfortunately, the MCP film is also a barrier to electron transport within the intensifier. Substantial enhancement of the image intensifier operating parameters is the motivation for the removal of the MCP film. This paper presents results showing for the first time that it is possible to fabricate a long lifetime image intensifier with a single uncoated MCP.
Fast-tunable filter for packet-switched broadcast-and-select all-optical network
Author(s):
Nina L. Taranenko;
Vladimir Katsman;
Richard Nottenburg;
Stephen C. Tenbrink;
Kevin Hsu
Show Abstract
A novel high-speed fiber Fabry-Perot tunable filter works fast enough (three orders of magnitude faster than commercially available ones) to allow packet switching for all-optical broadcast-and-select Wavelength Division Multiplexed network. Each node transmits at a Gb/s on dedicated wavelength over the passive-star coupler to all other nodes. The receiver at each node scans through all the wavelengths and selects signals addressed for that node.
Transverse mode selectivity of the Gaussian mirror in hollow-waveguide lasers
Author(s):
Piotr Witonski;
Pawel Szczepanski
Show Abstract
In this paper we analyze the losses in coupling radiation from the guide into the free-space and back, for waveguide laser resonator with Gaussian mirror. The laser characteristics showing the behavior of the total coupling coefficient, as a function of the curvature radius, Gaussian parameter and position of the Gaussian mirror are discussed. It is shown that for moderate values of the Gaussian parameter the Gaussian mirror provides transverse mode selectivity in hollow-waveguide structure and minimal coupling losses are obtained for the fundamental laser mode.
Measurements of optical gain in Nd3+-doped fluoroindate glasses
Author(s):
Glauco S. Maciel;
L. de S. Menezes;
Cid B. de Araujo;
Younes Messaddeq
Show Abstract
We report optical gain at 382 nm and 414 nm from Nd3+ doped fluoroindate glasses after excitation with lasers operating either at 583 nm or 532 nm. Stimulated emission due to a frequency upconversion process results in increase of the emitted light intensity and emission line narrowing. Large optical gain is measured by pump-and-probe spectroscopy using samples with various Nd3+ concentrations.
Surface profiling of an absorber embedded in a dense medium by spatial integration of the backscattered light
Author(s):
Toshiaki Iwai;
Gaku Kimura
Show Abstract
The new method to reconstruct the 2D surface profile of an absorber embedded in a dense scattering medium is proposed in the report. The method is based on the fact that the intensity of the multiply-backscattered light integrated spatially by the detecting aperture with finite size is directly related with the optical path-length distribution. Experiments and Monte Carlo simulations confirm the potential and the availability of the proposed method.
Real-time interferometric monitoring of dip coating
Author(s):
Flavio Horowitz;
Alexandre F. Michels;
Petrus A. Alcantara Jr.;
Marcelo Barbalho Pereira;
A. P. Rizzato;
C. V. Santilli
Show Abstract
First results are presented of optical interferometric monitoring during dip coating in real time, as applied to mineral oil OP10 and multi-component zirconyl chloride aqueous solution films. Resulting new perspectives are considered.
Two-photon absorption in Zn1-xMgxSe films grown by molecular beam epitaxy technique
Author(s):
Beata Derkowska;
Bouchta Sahraoui;
Grzegorz Glowacki;
Xuan Nguyen Phu;
Waclaw Bala
Show Abstract
The experimental results of nonlinear optical studies at 532 nm using picosecond pulses of Zn1-xMgxSe films are reported for x equals 7%, 16% and 40%. The effects of doping on linear ((alpha) ) and nonlinear ((beta) ) absorption coefficients are investigated. All studied samples reveal a relatively strong nonlinear absorption which decreases with an increase of Mg content. The undoped sample (0% Mg) displays absorption coefficients almost equal to those of the ZnSe crystal annealed at the same temperature.
Measurement of the nonlinear refractive index of materials with a single pulse
Author(s):
Mehrdad Mohebi;
Nooshin Jamasbi;
Alexandro Ruiz de la Cruz
Show Abstract
We present a single shot method of measurement of the nonlinear refractive index of materials. In this method a single laser pulse is used in a setup similar to the Z-scan technique. It is therefore as simple and sensitive as the z- scan. In this method unlike the Z-scan, the sample is fixed with respect to the lens while the focus position is scanned across the sample (F-scan). The far field transmission of the beam through an aperture is then measured. This method eliminates the need to move the sample in addition to the measurement error due to peak power fluctuations from pulse to pulse.
Spectrophotometric investigation of skin blood vessels on the basis of color perception
Author(s):
Yoshihisa Aizu;
Masaki Isokawa;
Tomonori Yuasa;
Hiromichi Mishina;
Toshimitsu Asakura
Show Abstract
This paper investigates spectral reflectance of blood vessels in a skin tissue phantom. Measured reflectance spectra are slightly influenced by the vessel diameter, depth from the surface, and oxygen saturation state. We discuss a possibility of extracting the information on blood vessels from the reflectance spectra on the basis of color perception using the dominant wavelength in the CIE xy chromaticity diagram with the pseudo-reference white. The results show the usefulness of this method.
Optical microtopographic inspection of thermoplastic rubber
Author(s):
Manuel Filipe M. Costa
Show Abstract
Shoe's industry has a major economical importance in Portugal. A tight quality control is necessary in any and all steps of the production process. The strength and quality of the gluing of the sole to leather are of major importance in the process of making a high quality shoe. This pasting process is standardized for different kinds of sole/leather combinations. However even if proceeding carefully problems due happen and specially as new kinds of sole's materials and leather' types are introduced in the production lines. A careful physical characterization of the gluing process as well as all items intervening is again necessary. On this communication we will present and discuss the results of the inspection process as well as the optical inspection system and inspection' procedure employed.
Imaging through scattering media using cameras and parallel processing
Author(s):
Sandrine Leveque;
Arnaud Dubois;
Emmanuel Beaurepaire;
Loic Pottier;
Albert Claude Boccara;
Martial Lebec;
Herve Saint-Jalmes
Show Abstract
Matrices of detectors carrying up to a few millions of pixels have changed in many aspects the science of imaging from astronomy to popular photography as well as from X rays to infrared. Most of the time they have been used for signal acquisition but rarely as an active part of the signal processing. A few years ago we have proposed ' touse such sensors, which convert radiations into charges and store them before reading, in order to achieve parallel lock-in or heterodyne detection at frequencies much higher than the speed of image acquisition. In the usual single channel lock-in detection scheme the (amplified) periodical noisy signal as multiplied by a noiseless synchronous reference signal and then filtered by a low-pass filter. In our approche 2 roughly speaking, the low-pass filter is replaced by the charge integration during one image acquisition whereas the multiplication is replaced by a synchronous excitation of the source (typically each half or quarter of period). Let us point out that the gain in term of signal-to-noise ratio is about the same in the two approaches (as long as we have to face a white noise such as the shot noise) but in the last one acquisition time can be i04 to iO times faster. In the two examples that we will describes below we will take advantage of the new promising field of biomedical imaging to demonstrate how helpful is our approach for imaging inside biological tissues which are strong light scatterers.
Thermal strain measurement of joint materials over a small spatial region using statistical interferometry
Author(s):
Hirofumi Kadono;
Hirofumi Kitajima;
Satoru Toyooka
Show Abstract
Statistical interferometry is applied to the measurement of thermal strain of object having an interface of two different materials. The technique is based on the statistics of the fully developed speckle field. The complete randomness of the speckle phase can play the role of a standard phase in a statistical sense, and the phase of the object under testing can be derived in a statistical way, in contrast to the conventional interferometry. In this study, the optical system is optimized to measure the thermal strain in a very small region around the interface of joint specimen. Experimental results show that the present method permits the measurement of strain with the accuracy approximately 10-6 with a spatial resolution > 50 micrometers .
Optical properties and green upconversion emission from Er3+-doped sol-gel silica glasses under red light (632.8-nm) excitation
Author(s):
Pham Nga Thu;
Van Hoi Pham;
Nguyen Xuan Nghia;
C. Barthou;
Vu Kim Lien;
Le Ngoc Chung;
Pham Nam Thang;
Nguyen Cong Trang
Show Abstract
The sol-gel process has been employed to prepare highly doped Er3+ silica glasses, up to 5-wt% for homogeneous doping distribution. The optical characteristics of the silica glasses including the UV/VIS absorption and fluorescence emission spectra under excitation of 488 nm and 520 nm lights were measured. Micro-Raman spectra of these silica glasses heated at different temperatures from 200 degree(s)C to 1100 degree(s)C under 632.8 nm laser beam excitation of the He-Ne laser also recorded. The green up conversion emission from Er3+ ion doped into the silica glasses heated to 1000 degree(s)C under red light (632.8 nm) excitation has been observed. Two green and weak emission bands, centered at 525 and 550 nm, for the 2H11/2 yields 4I15/2 and 4S3/2 yields 4I15/2 transitions, respectively, have been observed. The blue upconversion emission er3+ at 300 K centered at 460 nm was observed rather strength depends on the He-Ne laser pump powers and the Er3+ concentration. The pump wavelength is far from any electronic absorption from the ground state of the Er3+ ion, but corresponds to the excited state absorption. This upconversion process was interpreted by the excited state absorption and an upconversion mechanisms is proposed.
Near-infrared Faraday dispersion optical filter
Author(s):
Yundong Zhang;
Zhiwen Chang;
Yong Bi;
Zuguang Ma
Show Abstract
A near infrared potassium Faraday anomalous dispersion optical filter was theoretically studied for the transition, including hyperfine ef fects. In the paper the Zeeman splittings of potassium were calculate d for the given transition, that is, diagonalizing the disturbed matri x, and finding out the Zeeman sublevels position and transition freque ncies. Next we obtain an expression for the bulk polarizability tensor . Finally we acquire the transition coefficient relating to the polari zability tensor. The effect of temperature and magnetic field on prope rties of Faraday optical filter were investigated. The optimum filter operating condition was also obtained. The single peak bandwidth of th e optical filter is about 0.86GHz, equivalent noise band width is 2.4G Hz. The transmission is approximately 94.1 percent under the optimum c ondit ion.
Investigation of backscattered radiation by a crystal cloud to bistatic polarization laser sounding
Author(s):
Olga Vladimirov Shefer
Show Abstract
The crystal clouds extend above a mostly surface of the Earth. Their structure is submitted by a huge variety of forms and sizes ofparticles. According to conditions of crystal growth, one or other kind of particles prevails in a cloud'. The particles of the extended form such as polyhedrons, needles, plates were observed in all atmospheric formations essentially. The character of movement of particles in quiet layers of an atmosphere is caused by their aerodynamic properties and gravitational forces. Plate crystals are more tolerant on position in space among the extended formed particles. A behaviour of atmospheric particles depends on character of movement of airflow. The reorientation of each crystal will be determined by a difference of vectors of speed of its fall and speed of movement of a wind. All powerful fields influence on a circulation of airflow. A deep heterogeneity of the Earth, a breaks of geological structures, a fluctuation in magneticsphere, a electrical field influence on formation of atmospheric structure. As a rule, the presence of a powerful field is favourable to a steady position of particles in space. The numerous investigations have shown, that the ice clouds in the greater part consist of systems of particles of some primary orientation. The mechanism of light scattering on such crystals differs appreciably from scattering on spheres or chaotic oriented particles. Feature of light scattering by nonspherical particles is obviosly expressed anisotropy. It is possible to observe a anomalous optical phenomena in an atmosphere, as a consequence of radiation scattering on preferred oriented crystals.
Active imaging applied to navigation through fog
Author(s):
Wendell R. Watkins;
David H. Tofsted;
V. Grayson CuQlock-Knopp;
Jay B. Jordan;
Mohan M. Trivedi
Show Abstract
Navigation, especially in aviation, has been plagued since its inception with the hazards ofpoor visibility conditions. Vehicular ground movement is also hampered at night or in low visibility even with night vision augmentation because of the lack of contrast and depth perception. For landing aircraft in fog, the visible and near-infrared have been discounted because of the large backscatter coefficients in favor of primarily radar that penetrates waterladen atmospheres. Aircraft outfitted with an Instrumentation Landing System (ILS) can land safely on an aircraft carrier in fog. Landing at an airport with an ILS is not safe because there is no way to detect small-scale obstacles that do not show up on radar but can cause a landing crash. We have developed and tested a technique to improve navigation through fog based on chopped active visible laser illumination and wide baseline stereo (hyperstereo) viewing with real-time image correction of backscatter radiation and forward scattering blur. The basis of the approach to developing this active hyperstereo vision system for landing aircraft in fog is outlined in the invention disclosure ofthe Army Research Laboratory (ARL) patent application ARL-97-72, filed Dec. 1997. Testing this concept required a matched pair of laser illuminators and cameras with synchronized choppers, a computer for near real-time acquisition and analysis of the hyperstereo imagery with ancillary stereo display goggles, a set of specular reflectors, and a fog generator/characterizer. The basic concept of active hyperstereo vision is to compare the imagery obtained from alternate wings ofthe aircraft while illuminating only from the opposite wing. This produces images with a backscatter radiation pattern that has an increasing gradient towards the side with the illumination source. Flipping the imagery from one wing left to right and comparing it to the opposite wing imagery will allow the backscattered radiation pattern to be subtracted from both sets of imagery. Use of specular reflectors along the sides of the runway will allow the human stereo fusion process to fuse the forward scatter blurred hyperstereo imagery of the array of specular reflectors with backscatter eliminated and allow the appropriate amount of inverse point spread function deblurring to be applied for optimum resolution of scene content (i.e., obstacles on the runway). Results of this testing will be shown.
Temperature profile/fluctuations of a two-dimensional slot burner using laser speckle photography
Author(s):
Chandra Shakher;
Ruchi Vats;
S. K. Angra
Show Abstract
Double exposure speckle photography has been used for determining temperature profile of the burner. Further we have investigated single exposure speckle photography for measuring temperature fluctuations. These studies show that laser speckle photographic technique can provide complete solution to measure the temperature, temperature profile and temperature fluctuations around the mean value of temperature at any point of interest in the flame of burner. Experimental results of investigations made on 2D burner are presented.
Symmetry recognition in images
Author(s):
Kumar Eswaran
Show Abstract
This paper is concerned with the problem of separation of data, by a neural based computer recognition system. To this end certain types of data which are `tricky' are studied in order to see if they can be separated (i.e. classified) by a neural network or by a Kohonen based classifier. It is shown that there exist data which cannot simply be separated by a nearest distance classifier and yet can be treated well by a neural network, these correspond to the symmetry problem in images. In this paper the question that is posed and answered is: `If we are given a set of binary images, is it possible to devise an algorithm which will enable the computer to automatically recognize those images which have an inherent symmetry or near-symmetry?' It is demonstrated that a neural based algorithm can be trained to do the job efficaciously.
Er3+ and Er3+/Yb3+ co-doped silicate glass waveguides
Author(s):
Giancarlo C. Righini;
Marco Bettinelli;
Massimo Brenci;
Claire Duverger;
Maurizio Ferrari;
Matteo Fossi;
Maurizio Montagna;
Stefano Pelli;
Adolfo Speghini
Show Abstract
Integrated optical devices including rare earth ions are attracting an increasing attention. We designed and developed a soda-lime silicate glass matrix, suitable for ion-exchange, and we doped it with different percentages of Er2O3 and Yb2-O3. Optical waveguides have then been produced by diluted silver ion exchange. Here we report on their optical characterization, which has been performed by m-line spectroscopy as well by absorption, FTIR and Raman spectroscopy.
Innovative low-cost adaptive optics programs: a new mind-set emerges
Author(s):
Jeffrey T. Baker;
Jeffrey Foster Friedman;
Isabelle Percheron;
Lyle G. Finkner;
Sergio R. Restaino;
Gary C. Loos
Show Abstract
Gone are the days of unfettered government spending. An affordable, high performance alternative to multi-million dollar adaptive optics systems is required by the scientific and industrial communities. We have constructed and now give early performance specifications for the 1 St ofthree low cost Adaptive Optics systems for the University of Puerto Rico Imaging Interferometer. Built in months, not years, our in-house subsystem developments include (1) a photon counting ICCD Shack-Hartmann wavefront sensor; (2) a zero latency analog wavefront reconstructor; (3) a precision 2D geometry interpolator; (4) a 700Hz bandwidth beamsteering mirror system with photon counting tracker; and (5)adata acquisition, monitoring and deformable mirror control computer. Key to the control system is a 37-element MEM electrostatic membrane deformable mirror purchased from OKO Technologies. Every element of this system is innovative in the sense of exceptionally high performance at low cost. We will discuss the applicability of using several unique 2D liquid crystal spatial light modulators as correcting elements. We will discuss feedback vs. feed-forward implementations of control law, as well as many practical considerations of full implementation. Other possible medical, industrial, and scientific applications of this affordable, high performance AO technology will be presented.
Slitless rainbow holography
Author(s):
Arapbay Maripov
Show Abstract
Fundamental properties and particularities ofthe Gabor's,Leith-Upatnieks's and Denisjuk's holograms are well . TheBenton's rainbow hologram excites great interest .Benton's rainbow holography is a two-step process of hologramrecording where a narrow aperture slit is introduced into the second stage.One-step schemes for rainbow holography (RH) were proposed later on. A narrow aperture slit restricting object wave is an inherent component ofthe existing schemes of one- and two-step recording schemes. The aperture slit in RI-I recording schemes is the main disadvantage of RH method because it increases exposures 1 00 tol 000 times and prevents applications ofthis method in real time interferometry.. The united hologram uniting the Gabor's, Leith-Upatniecs's and Benton's holograms in one is considering in this report. This is the slitless method of RH recording. The report summarizes slitless one- and two-step methods ofRH recording. The narrow aperture slit is excluded in the slitless method of RI-I recording through application of the second reference wave coaxial with the object one. As a result, three holograms are being recorded simultaneously on a photographic plate: an axial Gabor's hologram, an off-axial Fresnel's hologram and a regular holographic grating (RHG), moreover, the off-axis and RHG possess the same spatial frequency. Existence of a RHG in a hologram is the cause of new features: object image is reconstructed in rainbow colours when such a hologram is illuminated with white light ;when it is illuminated with laser light a number of new object images. The report also shows the common physical nature of the phenomena that seems at first rather distant from each other: of rainbow holography and the Talbot effect in holography, and it proposes a theory of slitless RH and of the Talbot effect in holography developed from a unified point of view.
Online detecting ships in lock using optical flow method
Author(s):
Yulong Cao;
Mingwu Ren;
Jingyu Yang
Show Abstract
In the paper, an on-line detection system for ships in lock of is presented. The system has three functions: (1) Judging whether there are ships in lock in time; (2) Detecting whether ships cross the forbidden lines in lock; (3) Observing whether there are ships out oflock. Therefore, the system not only maintains the normal and fast working of lock,but also ensures safety of lock. The detection method is based on the optical flow of gray-level probability.
Fabrication of refractive microlens with coding gray-tone mask
Author(s):
Jun Yao;
Jingqin Su;
Yixiao Zhang;
Fuhua Gao;
Hui Wei;
Yongkang Guo
Show Abstract
The fabrication of refractive microlens by introducing the melting process with coding gray-tone mask is reported. The applied mask is obtained by the coding method, nonlinear effects in intensity distribution through the gray-tone mask have been taken into account to correct the mask design. A continuous relief is formed in photoresist after exposing, and then the excellent surface shape microlens can be gained by melting. The technical parameters of this process are also presented. Results are presented for experiments and evaluated by profile meter and scanning electronic microscope. The fabrication technology of refractive microlens by this process is simple and it indicates the enormous potential to extend the fabrication range ofrefractive microlens.
Blast wave interactions with structures using a phase-stepped double reference beam holographic interferometer
Author(s):
Silvia M. Booij;
Louk H.J. Absil;
Anastasius J.A. Bruinsma;
Joseph J. M. Braat;
Hedser H. van Brug
Show Abstract
One of the main activities of the Explosion Prevention and Protection Research Group of TNO is the quantification of explosion effects and the prediction of possible consequences. The research presented is aimed at setting up new guidelines for safety distances for urban areas around hazardous sites. To investigate the distribution of the blast load on buildings experimentally, the buildings are scaled down and exposed to a plane shockwave in a 40x40 cm2 shock tube. For perfect gasses the Hopkinson scaling law applies. This law states that if all characteristic times are scaled by the same factor as the length scale then all pressures, temperatures, densities and velocities will remain unchanged. In the shocktube the shockwave will propagate and interact with objects. The density distribution around the objects can be visualized using an interferometer and from the interferograms the pressure distribution can be computed. These data can be used to validate numerical results obtained with the Computational Fluid Dynamics code BLAST. This code, developed at the Prins Maurits Laboratory of TNO, simulates the interaction of three-dimensional blast waves with structures. The data obtained can be used for the accurate prediction of the blast load on individual buildings in an urban area. In the tests, rectangular blocks were used to obtain the two dimensional test situation shown in figure 1 .At some typical locations on the structures, the pressure signal was measured by means of piezo-resistive pressure-transducers. Interferograms were recorded using a phase-stepping double-reference-beam holographic interferometer. The principle of the interferometer setup is that the initial state and the disturbed state are both recorded on one single holographic plate, using two slightly tilted reference beams. When analyzing, the two reference beams simultaneously reconstruct the initial state and the disturbed state. The two states will interfere and the resulting interference pattern is recorded using a CCD camera. This interferometer setup is very attractive because, first of all, it is possible to record an interference pattern hardly influenced by the mechanical vibrations caused by the shock tube, secondly, this interferometer is easy to setup, and thirdly, most lens errors cancel out in the resulting image because of the double reference beam. A typical example of a reconstruction of an interferogram recorded with the holographic interferometer is shown in figure I. where the shockwave travels from the left to the right, interacting with two models of buildings. To be able to calculate tile pressure distribution, more than one reconstruction of the interferogram is needed. If the difference in optical pathlength between the reference beams is varied over an unknown, but constant, distance, at least four reconstructions are needed. From four different recordings the pressure distribution can be calculated. First, all pixels that do not have enough contrast are being removed, then the phase is calculated, for example using Carré's algorithm, the result of this can be seen in flgure 2. Subsequently the discrete 271 steps have to be removed, which is called phase unwrapping, and finally the grey values in this image have to be converted to pressure values. The resulting pattern of isobars can be seen in figure 3.This image can be compared to tile numerical simulation in figure 4 that was obtained using the BLAST-code. ibis paper presents an optical study of blast wave propagation and interaction with multiple structures and a method for obtaining quantitative information on the pressure distribution from a number of phase-stepped images.
Design of the two-dimensional spectrograph
Author(s):
Guofeng Song;
Guoxiang Ai
Show Abstract
The principles ofTwo.Dimensional Spectrograph (TDS) fbr the Space Solar Telescope (SST) arc described in this article. The TDS will be the main focus plane instrument of thc payload of SSL It is a kind of birefringent filtcr with polaroids replaced by polarizing beam spliLter. It permits observations of solar. vector magnetic field or lincof-sight velocity fields in any Fraunhofcr line in the wavelength region from 3900 in 6600 angstrom with half width horn 0.03 to 0.12 angstrom. Lt can be turned across the spectral line to obtain linc profiles ofiwo-dirnensional field of view in one channel and also van be turned on one spectral line to obtain partofthe line profiles of two-dimensional field of view with 8 channels. This article also describes the analysis of mechanicul and thermal control of the TDS. In the finale, a new polarimeter of this system is introduced.
Axicons with a dark spot on axis
Author(s):
Jose A. Soto-Sanchez;
Jorge Ojeda-Castaneda
Show Abstract
We present a family of diffractive binary screens that encode a new type of optical axicons, which generate a dark spot along the optical axis. We report experimental verifications showing the usefulness of these devices in optical alignment.
Optimization of output power in circular-grating DBR and DFB lasers
Author(s):
Tomasz Kossek;
Pawel Szczepanski;
Piotr Witonski;
Michal Malinowski
Show Abstract
In this paper we present the systematic numerical studies of nonlinear operation of planar waveguide DBR/DFB lasers with circular grating. An approximate formula relating small signal gain to the output power and the parameters of the structure characteristics for this kind of laser is derived. Laser characteristics obtained revealing gain saturation effects can be used for design optimal structure providing maximal output power for the given pumping rate of the laser medium.
Micro-electro-mechanical deformable mirrors for advanced adaptive optics applications
Author(s):
J. Y. Decker;
Scot S. Olivier;
James A. Folta;
William D. Cowan
Show Abstract
Adaptive optics technology is critical for many current and developing applications at Lawrence Livermore National Laboratory. In particular, most large laser systems, including those being developed for Inertial Confinement Fusion and Laser Isotope Separation, require adaptive optics to correct for internal aberrations in these high-power systems. In addition, adaptive optics can provide capability for both high-resolution imaging and beam propagation through the atmosphere. Requirements for laser systems, imaging and propagation applications are currently driving wavefront control technology toward increased spatial and temporal frequency capability, as well as reduced system costs. We will present recent progress in the development of micro-electro-mechanical deformable mirrors for adaptive optics applications.
Volume holographic memory with a speckle-encoded reference beam
Author(s):
Vladimir B. Markov;
James E. Millerd;
James D. Trolinger
Show Abstract
Important advances of holographic memory. such as parallel input-output, high data transfer rate and ultimate density for optics storage have attracted a lot of interest. The principal feature of volume holography (known as very high selectivity of the diffracted beam intensity to reference beam deviation) is typically used for data multiplexing. Thus, most common techniques for data sampling are based on angular' and spectral2 selectivity resulting from the momentum conservation law (Bra law) for volume holograms3. Angular selectivity has been used more often as it is simpler to implement in practice. It was demonstrated4.5 that data multiplexing with up to 10.000 pages of information can be stored in one crystal as write-read/erase or read-fix. Refextnce bean arbitrary phase encoding also was demonstrated as a useful technique for this purpose, although the detailed analysis of the method was limited only by the conditions where the profile modulation across the reference beam was altered by arbitrary encoding. The first demonstration of shift selectivity of thick holograms with a speckle encoded reference beam was reported7, and later a theoretical explanation of the observed peculiarities8 was given suesting this type of selectivity for high density data storage9. A similar approach was suested for volume holograms with a spherical reference wave;10 however the existing methods do not explore the possibility of the effective use of an entire volume of the hologram as suested in the development for optical disc memory systems11. In this report we present the results of volume hologram recording with high density data obtained through a real volumetric encoding method that allows an increase in the data storage density.
Image segmentation with a white light optical correlator
Author(s):
J. Barbe;
Juan Campos
Show Abstract
In this paper we propose an optical system to perform the segmentation of an input scene based in its frequency contain. The system is an optical correlator illuminated with a white light lamp. The final image is detected by a 3CCD camera to perform the separation of the channels. Selecting the spectral transmittance of the filter for the different zones the segmentation of the input image can be performed.
Multibeam Fizeau interferometer image plane
Author(s):
Yuri N. Zakharov
Show Abstract
Fizeau interferometer pattern analysis have carried out in the case of arbitrary slope beam illumination. Analysis get localization plane location (that is in coincidence with image plane) and its dependence on wedge relative index of refraction and on the interferometer entrance mirror slope angle to the incidence wave. The analyses fits experiment.
Surfaces analysis based on subfringe integral method
Author(s):
Iza Melao;
Edison Goncalves;
Mikiya Muramatsu
Show Abstract
This work shows the most used techniques for fringe analysis and presents a novel technique based on sub-fringe integral method with carrier frequencies, for phase retrieval. This method integrates one fringe into various subfringes to obtain the phase value. Several experiments were performed to obtain the information of flatness and profile from the surface to be analyzed.
Optical stark splitting of the absorption spectrum of Rhodamine 101
Author(s):
Aristides Alfredo Marcano O.;
Ines Urdaneta
Show Abstract
We measure the absorption spectrum of an ethanol solution of Rhodamine 101 in the spectral region 555 nm - 585 nm as a function of the incident light fluence. Distortions of the absorption spectra are observed at high fluence values. Besides the observation of the light induced spectral broadening, we report the splitting of the spectrum into two peaks as predicted by the optical Stark effect theory.
Use of image quality metrics for correction of noncommon path errors in the ELECTRA adaptive optics system
Author(s):
Nathan P. Doble;
Gordon D. Love;
David F. Buscher;
Richard M. Myers;
Alan Purvis
Show Abstract
The technique of image sharpening was first proposed by Muller and Buffington'in 1974. This work was furthered by O'Meara2 and more recently by Brigantic3. The technique is very simple and lends itself to the correction of slowly varying or static aberrations. The basic methodology is as follows;
1) Measure the system PSF or the aberrated image.
2) Characterise the image by means of an image metric. This metric will give one figure, which describes the 'quality' of the image.
3) Apply a trial correction to the wavefront corrector.
4) Reassess the image quality metric.
5) If the metric increases apply more of the same correction, if not stop and move on. Repeat until best image is achieved.
A problem lies in how do we define the 'quality' of an image through the use of a metric. There are two general requirements:
An image metric takes on the maximum value when the system is aberration free.
• The image metric needs to be calculated in a time period that is shorter than any temporal evolution of the aberration.
Time multiplexing superresolution optical system with computer decoding
Author(s):
Amir Shemer;
David Mendlovic;
Zeev Zalevsky;
Adolf W. Lohmann;
Javier Garcia;
Emanuel Marom
Show Abstract
Objects that temporally vary slowly may be super resolved using two moving masks such as pinhole or grating. A system of that kind had been previously proposed by Francon and Lukosz. Later on an improvement was obtained by using specially designed Dammann gratings. These approaches require two gratings, one at the object plan and the second at the detectors plane. In this project, the second is replaced by a computer. This way, the synchronization problem existing when two gratings are used in simplified. The method can be applied for both coherent and incoherent illuminations.
Self-mixing superluminescent diode optical tomography
Author(s):
Luigi Rovati;
Franco Docchio
Show Abstract
In the self-mixing super luminescent diode (SM-SLD)1 technique the monitor photodiode is exploited to detect the interference signal. The major advantage of this techniques is that the interference signal is optically amplified by the high-gain active medium making its detection more simple and enhancing SNR. The major drawback is the amplification of the interference satellite subpeaks which degrade LCI perfonnance.
High-speed and high-resolution heterodyne interferometer using a three-mode laser
Author(s):
Toshiyuki Yokoyama;
Tsutomu Araki;
Shuko Yokoyama;
Norihito Suzuki
Show Abstract
In the measurement using conventional heterodyne interferometer, `high-speed' and `high-resolution' were methodologically contradictory problems. Previously, authors have solved this contradiction by using two conjugate beat signals. In this work, we realized highly sensitive measurement without speed limit of the target using a three- mode laser. The synthetic wavelength of (lambda) /2 generated by three-mode laser enabled to increase the measurement sensitivity twice. The three-mode laser also has an advantage of higher output power.
