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- Front Matter: Volume 9654
- International Conference on Optics and Photonics 2015
Front Matter: Volume 9654
Front Matter: Volume 9654
Show abstract
This PDF file contains the front matter associated with SPIE Proceedings Volume 9654 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.
International Conference on Optics and Photonics 2015
White light interferometer: applications in research and industry
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Applications of interferometer are countless both in the research and commercial world. Laser sources offer precise
measurements of relative path difference between two interfering beams. An exciting example is LIGO (laser
Interferometer for Gravitational Observatory), which is aiming to resolve length change as small as 10-19 m over a 4 km
length for detection of gravitational waves. However, laser is a disadvantage for microscopic imaging and surface
topography applications usually required in semiconductor industry. A different approach for microscopy is to use white
light in place of laser. White light due to its limited temporal coherence offers a multitude of benefits for imaging
applications. An immediate benefit from white light is the sharp localisation of interference fringe that makes the 3D
topography construction or OCT (Optical Coherence Topography) realisable using a Scanning White Light
Interferometer (SWLI) imager. In Mirau Mode, SWLI performs high resolution imaging; whereas in Michelson mode
Fourier Transform Spectroscopy (FTS) is realised. SWLI can easily be modified into PUPS (Pupil Plane SWLI) for
Ellipsometry. Superimposing Michelson Interferometer known as VISAR (Velocity Interferometer System for Any
reflector) can form interference fringes even in presence of wide angle light scattered from a moving illuminated object.
This paper describes work undertaken at Nanometrics (UK) on simulation of SWLI fringes including high Numerical
Aperture (NA) applications, thin film characterisation, OCT generation and Zemax modelling of compact dispersion-free
vibration-immune Fourier-Transformed spectrometer. VISAR as a modified Mach-Zehnder Interferometer is also
discussed based on the work at Rutherford-Appleton laboratory (UK).
Writing with lasers: a new technique of controlled lithography using thermooptically manipulated microbubbles
Show abstract
We have developed a new technique of optical micro-patterning using micro bubbles based on light induced self-
assembly of materials using thermo-optic tweezers. Presently, we use a liquid matter- Soft Oxo-Metalate (SOMs)
that have high absorption near the wavelength of the tweezers laser at 1064 nm. An aqueous dispersion of the
sample solution is taken in a glass sample chamber and introduced into the translation stage of our tweezers
set-up (inverted microscope) where a highly focused laser beam is aimed at SOM particles adsorbed on the top
surface of the sample chamber. The high absorptivity of SOMs ensures the creation of a local `hot-spot' which
leads to the nucleation of a micro-bubble in this region. Thus, a large local surface-tension gradient is introduced
in the vicinity of the micro-bubble due to the temperature gradient produced at the two ends of the bubble, which
leads to a Marangoni type convective
ow around the bubble. This
ow causes material to be self-assembled
at the base of the bubble. As the translation stage is moved, the `hot-spot' moves simultaneously, and due
to the resulting
ow dynamics, the microbubble is also translated thus causing continuous accumulation of the
SOMs around it. Simultaneously, due to the sudden thermal shock generated when the `hot-spot' is moved away
from the self-assembled SOMs, they undergo a phase transition from soft (liquid) to hard (crystalline) state,
resulting in the formation of a stable permanent pattern of choice on the glass substrate. This technique can
have diverse applications with materials other than SOMs including carbon nano tubes, organic dyes, catalysts
and conducting polymers, etc, being co-deposited from aqueous dispersions of the particular material with the
SOMs. The patterns thus formed have been used for various applications including the development of catalytic
micro-chips, and solution processed printable micro-circuits.
Plasmonics-integrated Ge PIN-photodetectors: efficiency enhancement by Al nanoantennas and plasmon detection
Show abstract
The aim of integrating plasmonic functionality with photonic devices is twofold: on the one hand, plasmonic
nanoantennas can enhance the functionality of photonic devices and enable their miniaturization. On the other hand,
photonic devices can be a part of plasmonic transmission lines and act e.g. as plasmon detectors. Here, we present results
on both aspects in a CMOS-compatible device setup using Ge PIN-photodetectors and Al nanostructures. Plasmonic
nanoantennas are metallic nanostructures that enable the control and manipulation of optical energy in the visible and
near-infrared spectrum and have been proposed as a means to enhance absorption and quantum yields for photovoltaics,
to increase spatial resolution for optical microscopes and to enhance the energy efficiency of light-emitting devices. We
present experimental results on the enhancement of Ge PIN-photodetector efficiency by Al nanoantennas. In order to
investigate plasmon waveguiding and detection, metal grating structures and metal-insulator-metal slot waveguides were
fabricated by electron beam lithography in the Al metallization layer of Ge PIN-photodetectors. Photocurrent maps of
the devices under local illumination show that plasmons can be optically excited at the grating and are then guided by the
slot waveguide towards the Ge PIN-photodetector where they are detected as photocurrent. Using Ge PIN-photodetectors
and Al nanostructures as a CMOS-compatible device setup, we show how plasmonic nanostructures can be used for
efficiency enhancement of photonic devices and discuss plasmon detection with Ge PIN-photodetectors with possible
applications.
Self-similarity in Walsh filters and wave-optical engineering
Show abstract
The set of orthogonal Walsh filters consists of groups, members of which are self-similar. The corresponding axial and
transverse intensity distributions in the farfield diffraction patterns of these filters possess self-similarity. Results of our
investigations on the same are presented.
Measurement constraints in laser based thermal lens experiments
Show abstract
Importance of various measurement schemes in studying thermal lens (TL) signal for laser based TL experiments is
explored. We show that two different measurement schemes can result in two contrasting outcomes. In one
experiment, two measurement schemes show diverging results for TL signal measurements, which gives a
convoluted result and in the other experiment, the two measurement schemes give a converging result.
Imaging characteristics of a birefringent lens with primary spherical aberration under broadband illumination
Show abstract
This paper reports the imaging behavior of an optical system consisting of a uniaxial birefringent lens sandwiched
between two linear polarizers suffering from primary spherical aberration. The optic axis of the birefringent crystal is
perpendicular to the lens axis. The said system is illuminated with a polychromatic beam of light having flat-top spectral
profile and the quality of image formed by the system is evaluated by means of the intensity point spread function (IPSF)
and optical transfer function (OTF). The proposed system has high tolerance to primary spherical aberration under
broadband illumination.
Analytical modelling of Thirty Meter Telescope optics polarization
Show abstract
The polarization introduced due to Thirty Meter Telescope (TMT) optics is calculated using an analytical model. Mueller matrices are also generated for each optical element using Zemax, based on which the instrumental polarization due to the entire system at the focal plane is estimated and compared with the analytical model. This study is significant in the estimation of the telescope sensitivity and also has great implications for future instruments.
One to one coherent imaging through double and single hololens configurations: a comparative study
Show abstract
In this communication a comparative study of one to one coherent imaging through double and single hololens
configurations have been presented. Resolutions using the two imaging configurations are found to be 28 and 32
lines/mm respectively.
Amplitude filters in shaping the point spread function of optical imaging systems
Show abstract
We present our studies on apodization of pupils with various amplitude filters with respect to images of point
objects. The central intensity distribution, first maxima and first minima are compared with and without
apodisation. The effects of aberrations and aperture obscuration are also studied. It is shown that in certain
cases, the aberrated images can be improved with the help of suitable amplitude filters.
Design and optimization of high reflectance graded index optical filter with quintic apodization
Show abstract
Rugate filters are a special kind of graded-index films that may provide advantages in both, optical performance and
mechanical properties of the optical coatings. In this work, design and optimization of a high reflection rugate filter
having reflection peak at 540nm has been presented which has been further optimized for side-lobe suppression. A
suitable number of apodization and matching layers, generated through Quintic function, were added to the basic
sinusoidal refractive index profile to achieve high reflectance of around 80% in the rejection window for normal
incidence. Smaller index contrast between successive layers in the present design leads to less residual stress in the thinfilm
stack which enhances the adhesion and mechanical strength of the filter. The optimized results show excellent side
lobe suppression achieved around the stopband.
Modeling the segmented primary for a 10-meter-class telescope
Show abstract
The primary mirror for a 10 meter class telescope will be made of many individual segments rather than a
monolithic mirror, because of the ease with which the segments can be made, transported and replaced. An
f1 primary mirror with an RoC of 20 meter is modeled using Zemax. The theoretical evaluation of the basic
properties of the individual segments such as dimensions, orientation and location, has been carried out. The
dimensions of each segment is different because the primary mirror is curved and aspheric. These parameters
are further optimised with respect to the image spot size and also to minimise the narrow, uniform gap between
the segments. The results of this optimisation is discussed in this paper.
Near ultraviolet spectrograph for balloon platform
Show abstract
Small and compact scientific payloads may be easily designed constructed and own on high altitude balloons. Despite the fact that large orbital observatories provide accurate observations and statistical studies of remote and/or faint space sources, small telescopes on board balloons or rockets are still attractive because of their low cost and rapid response time. We describe here a near ultraviolet (NUV) spectrograph designed to be own on a high{altitude balloon platform. Our basic optical design is a modified Czerny-Turner system using off the shelf optics. We compare different methods of aberration corrections in such a system. We intend the system to be portable and scalable to different telescopes. The use of reflecting optics reduces the transmission loss in UV. We plan on using an image intensified CMOS sensor operating in photon counting mode as the detector of choice.
Broadband antireflection coatings for multifunctional avionic displays
Show abstract
Broadband Multilayer Antireflection (AR) coatings markedly improve the transmission efficiency of any optical
component such as lens, prism, beam-splitter, beam combiner or a window. By reducing surface reflections over a wide
wavelength range, broadband antireflection coatings improve transmission and enhance contrast which is desired in
avionic displays. The broadband antireflection coating consisting of MgF2, ZrO2 and Al2O3 were designed to cover the
whole visible spectrum and fabricated on optical grade glass substrate. The optical characterization of these coatings
indicates reduction of the reflection to 2.28% as compared to 8.5 % at 545 nm (i.e. design wavelength of most avionic
displays) for bare substrate making them useful in optical displays for avionic applications.
Multi-layer dielectric thin-film optical filters for beam folding applications
Show abstract
Multi-layer reflective thin film filters optimized for oblique incidence angles were deposited on glass substrates using
Electron Beam evaporation technique with in situ thickness monitoring. The present study involves deposition and
optical characterization of 5 layered multi-layer structures of TiO2-Al2O3 and TiO2-SiO2 having different thicknesses for
varied wavelength ranges in the visible region. Three TiO2-SiO2 multi-layer thin film filters were deposited having peak
reflectance at 480 nm, 540 nm and 675 nm respectively corresponding to light sources in the blue, green and red
wavelength regions. Similarly, a TiO2-Al2O3 multi-layer was fabricated having peak reflectance of around 64% at
610nm. These filters were deposited at an elevated temperature of 250° C in an oxygenated reactive environment for
better adhesion, mechanical strength and proper stoichiometry. Reflectance measurements of these multi-layer filters at
oblique incidence angles reveal high reflectance of around 70 ~ 75% with a reasonably broad reflection band which can
have wide applications in beam steering, shaping and folding applications in various complex optical systems facing
constrained space and weight requirements.
A co-phasing technique for segmented mirror telescopes
Show abstract
In the new era of astronomy, we go for bigger telescopes having segmented primary and secondary mirrors. But once
segmentation is done, aligning and phasing mirror segments so that altogether they act like a monolithic mirror of a large
diameter, becomes critical. Co-phasing is a complex task that needed to be done after aligning the segments. Diffraction
limited resolution is only possible by a large segmented telescope, if mirror segments are co-phased. Co-phasing techniques
rely on physical optics and in one of the technique implemented in Keck telescope is based on analysis of diffraction pattern
generated by Shack Hartmann sensor. This same technique is being further explored by us in laboratory experimentation.
In this paper we present our effort to develop a simple but robust phasing technique for a large segmented mirror telescope
proposed to be installed in India. After rigorous mathematical exercise , analytical formulation for the phasing technique is
derived, which is further used to simulate in MATLAB. The MATLAB results are cross checked with the ZEMAX. There
after, a preliminary laboratory experiment has been conducted to check the feasibility of using this technique for phasing
segmented mirrors.
Optics design of laser spotter camera for ex-CCD sensor
Show abstract
Development of Laser based instruments like laser range finder and laser ranger designator has received prominence in
modern day military application. Aiming the laser on the target is done with the help of a bore sighted graticule as
human eye cannot see the laser beam directly. To view Laser spot there are two types of detectors available, InGaAs
detector and Ex-CCD detector, the latter being a cost effective solution. In this paper optics design for Ex-CCD based
camera is discussed. The designed system is light weight and compact and has the ability to see the 1064nm pulsed laser
spot upto a range of 5 km.
Two-channel imaging system for the White light Active Region Monitor (WARM) telescope at Kodaikanal Observatory: design, development, and first images
Show abstract
One of the three planned back-end systems for the proposed National Large Solar Telescope (NLST) is the Solar Dynamics Imaging System (SDIS) which is intended to obtain near simultaneous images in multiple wavelengths. As a first step, a prototype system with two channel imaging has been developed and installed at the back-end of the White light Active Region Monitor (WARM) telescope at Kodaikanal Observatory. A two-mirror Coelostat serves as a light feeding system to a refracting objective while an optical breadboard serves as a platform for the back-end instruments. A re-imaging system is used before the prime focus to get two light channels for the observations in two wavelengths. The re-imaging system is designed using ZEMAX and the alignment of the system is done using a laser. Full disk images are obtained using a red filter (674.2nm/10nm) and a G-band filter (430.5nm/0.84nm). Design aspects of the re-imaging system, preliminary observations and image reduction methods are described in this paper.
Spectral characterization of Fabry-Perot etalon operating in Short Wave Infra-Red (SWIR) region
Show abstract
A promising technique for precise spectral characterization of solid Etalon operating in SWIR wavelength is
demonstrated using tunable laser with a minimum wavelength scan step interval of 1 picometer. Measurement is carried
out for 1640nm - 1660nm, an important region containing greenhouse gas absorption spectra. The etalon considered for
characterization is made of fused silica. The thickness is nearly 346 micron with physical diameter of 25.4 mm and clear
aperture of 23 mm. The etalon has a finesse of 7.25 and extremely narrow bandwidth like 0.4 nm or 400 picometer. The
measurement was as well carried out with an Optical Spectrum Analyzer (OSA). The conventional OSA instrument had a
resolution of 80 picometer limiting the measurement capability to detect a spectral shift as fine as 50 picometer. Also the
measured bandwidth had an error of ± 40 picometer over a spectral bandwidth of 400 picometer which is nearly ±10 %.
This leads to the use of a tunable laser exhibiting a provision to vary the wavelength at a step of 1 picometer. This
method provides measurement accuracy at least 4 times better than the earlier method. Accuracy may be further improved
by making the wavelength scan step interval even finer. The absorption due to presence of greenhouse gas like methane is
higher for the etalons with narrower bandwidth. This method can provide very good accuracy for characterization of
etalons with spectral bandwidth as narrow as 50 picometer.
Modulation of Moiré pattern using birefringent sample
Show abstract
Moiré pattern, produced by the overlapping of two radially sheared beams emerging from two longitudinally shifted
focal points of a birefringent lens has been experimentally demonstrated. Coherent and incoherent Moiré patterns are
generated with and without analyzer. Birefringent samples like mica sheets with opposite crystal axis to that of the
birefringent lens modulate the Moiré pattern. Mica sheet of different thicknesses have been used to demonstrate the
effect of thickness on phase retardation, hence on fringe pattern. Experimentally birefringence has been calculated by
fringe analysis and compared with theoretically simulated birefringence.
A simple method to measure refractive index of optical glasses using focal displacement method
Show abstract
A method is presented to measure refractive index of a plane parallel plate of optical glass. We have applied focal
displacement method to measure refractive index of a plane parallel plate of an optical glass having thickness of the
order of millimeters. The best focus position is found by applying edge detection algorithm. We have measured LAF2
optical glass using focal displacement method and obtained the value 1.746, which is within 0.1% of the standard value
1.747 at 555 nm. In comparison to Abbe refractometer, this method is simple in terms of sample preparation,
experimental set up and for measuring high refractive index of Zinc Sulfide. Using this method, refractive indices of
other optical glasses are also measured.
An experimental investigation on the influence of machining parameters on surface finish in diamond turning of silicon optics
Show abstract
Silicon is widely used in IR optics, X-Ray optics and electronics applications. These applications require Silicon of
optical quality surface as well as good form accuracy. To get the desired finish and dimensional accuracy, diamond
turning is preferable. Taylor-Hobson Nanoform-250 diamond turning equipment is used to machine flat Silicon mirror.
Negative rake diamond tool is used with a tool nose radius of 1.5 mm. A series of SPDT machining operations are
performed in the sequential combinations of tool feed rate, Spindle Speed and depth of cut. In order to find out the effect
of machining parameters on the Surface Roughness during turning, Response Surface Methodology (RSM) is used and a
prediction model is developed related to average Surface Roughness (Ra) using experimental data. The surface quality is
analyzed in terms of arithmetic roughness (Ra) and Power Spectral Density for uniform evaluation. In addition, a good
agreement between the predicted and measured Surface Roughness is observed.
Edge enhancement of phase objects using a cyclic-path polarization interferometer
Show abstract
The aim of this study is to model edge enhancement effect in purely phase samples. A self compensating interferometer
similar to Sagnac’s, employed with a polarizing beam splitter where two counter propagating orthogonally polarized
mutually coherent beams are modulated by the phase shifts introduced by a phase sample. An afocal imaging system is
used to image the phase sample on the CCD so that one of the images is slightly defocused. Real-time subtraction of two
images results in intensity modulation of phase interfaces.
A study of material removal response of various glasses in computer controlled sub-aperture polishing
Show abstract
Significant advances have been made in the field of fabrication of optical components over the years. While plano and
spherical surfaces are polished mostly by full aperture polishers made of pitch or polyurethane pads, no such approach is
possible for aspheric surfaces as polisher needs to conform to the changing local curvature of aspheric surface. For such
aspheric and freeform surfaces sub aperture polishing is a very attractive option as it forms a small polishing spot over
the surface of the optics and the path of this spot in multi axis configuration is precisely controlled by the computer. This
polishing process follows a deterministic approach and material removal information is very much necessary to control
surface form or surface accuracy of the optical component. Here we have carried out the polishing of several glass
substrates to find out the response of various glass types to this polishing process.
HOE for recording off-axis holograms of phase objects
Show abstract
Holographic optical elements (HOEs) play important role in realization of compact and cost effective systems. Use of
HOE not only give above mentioned advantages but an HOE can also be used to design and develop unusual system
configurations which may not be possible, at all, using the concepts of conventional optics. Present paper describes
fabrication of an HOE which contains both, reference and object, beams required for recording an off-axis hologram of
phase objects. Illumination of HOE with a collimated beam generates two spatially separated collimated beams which
intersect each other in the hologram recording plane. This combined HOE reduces a large number of opto-mechanical
components and alignment related issues, generally encountered in off-axis holography. Fabrication of HOE and
recording of holograms of phase objects using the HOE is described and experimental results of reconstructed holograms
are presented.
Non-invasive detection of periodontal loss of attachment using optical coherence tomography
Show abstract
This study aims at developing a non-invasive technique to evaluate periodontal loss of attachment in the oral cavity.
A method of imaging periodontal loss of attachment based on time-domain optical coherence tomography is proposed
and studied. Based on measurements, boundaries of gingival tissue and tooth were seen separated by ≈0.3 mm. Further
study is in progress to image the anatomical landmarks and evaluate the periodontal loss of attachment. The conventional
time domain OCT systems acquisition speed is limited by the speed of the mechanical scanning system. In order to
overcome this issue, a novel electro-optic based scanning system is proposed and demonstrated. Studies were performed
initially with lithium niobate and potassium titanyl phosphate crystals and the tuning range observed were low. In order
to increase the tuning range, a crystal with high electro-optic coefficient – potassium tantalite niobate was identified and
experiments were carried out to characterise the crystal and electro-optic based phase tuning is demonstrated.
Incipient fault diagnosis of power transformers using optical spectro-photometric technique
Show abstract
Power transformers are the vital equipment in the network of power generation, transmission and distribution. Mineral
oil in oil-filled transformers plays very important role as far as electrical insulation for the winding and cooling of the
transformer is concerned. As transformers are always under the influence of electrical and thermal stresses, incipient
faults like partial discharge, sparking and arcing take place. As a result, mineral oil deteriorates there by premature
failure of the transformer occurs causing huge losses in terms of revenue and assets. Therefore, the transformer health
condition has to be monitored continuously. The Dissolved Gas Analysis (DGA) is being extensively used for this
purpose, but it has some drawbacks like it needs carrier gas, regular instrument calibration, etc. To overcome these
drawbacks, Ultraviolet (UV) -Visible and Fourier Transform Infrared (FTIR) Spectro-photometric techniques are used as
diagnostic tools for investigating the degraded transformer oil affected by electrical, mechanical and thermal stresses.
The technique has several advantages over the conventional DGA technique.
Edge enhancement in digital holo-microscopy
Show abstract
A simple edge enhancement technique in the digital holo-microscopy is presented here. In Digital Holo-microscopy
(DHM) the intensity distribution of the CCD is produced by the interference of a plane reference wave and that
scattered by the object. The reconstruction is accomplished by multiplication of the digitally stored hologram with a
digital model of the reference wave and subsequent numerical determination of the diffracted field of the object in a
defined image plane. Hence, a focused and a defocused version of the object may be reconstructed from only one
recorded hologram by varying the reconstruction distance during numerical reconstruction. The edge enhancement
of the object is possible by simply subtracting this numerically reconstructed defocused real image from the focused
real image. It is interesting to note that using this technique edge enhancement technique is possible for amplitude
and phase objects. The simulation and experimental results presented validate our theoretical expectations.
Development of in-line laser interference microscope
Show abstract
Interference Microscope with exception of the widely used Mirau objective, involves a setup having Michelson
or Mach-Zender Configuration. The present work proposes an in-line interference laser microscope
configuration.
In process metrology of aspheric optical surfaces during sub-aperture polishing process
Show abstract
The fabrication of complex aspheric and freeform surfaces are possible with accurate iterative metrology feedback
during correcting polishing process. The tool path of the machine is generated based on the measured surface data
for corrective material removal. The computer controlled polishing machines are compatible with various metrology
tools. This paper presents annular null based interferometric in- process metrology for deterministic corrective
polishing for aspheric surface of infrared optical material.
Measurement of impurity in water using Talbot interferometry
Show abstract
Present communication reports investigations undertaken towards testing applicability of Talbot interferometry for
measurement of impurity in water. Because of presence of impurities in water, the refractive index of the sample (water)
changes. The variation of refractive index is mapped as change in the fringe order of the Talbot interferometric fringes.
Experimental investigation with ethanol and salt water as impurities has been reported. High accuracy and precision has
been achieved.
Opto-fluidic flow analysis for monitoring of immunity levels
A. Mohan,
A, Bharadwaj,
N. Marshkole,
et al.
Show abstract
We describes the design, development and testing of a cost effective and miniaturized version of a flow analyzer. It is designed to detect fluorescence labeled immunocytes in human blood sample. Availing of advancements in micro fluidics and nanolithographic technique, we fabricated a PDMS based device with integrated micro channels for accommodating the optical fibers. The lensed fibers serves as the waveguides for illumination and collection of laser and scattered signals respectively. As a cell crosses the interrogation point the forward scatter, side scatter and fluorescence are detected. Photomultiplier tubes used in conventional flow cytometers have been replaced here with APDs (avalanche photo detectors) and supplemented with digital signal processing. The prototype was tested with different sized polymer beads as well as the live cells.
Modeling and performance analysis of chalcogenide prism based plasmonic biosensor comprising of gold nanoparticle film
Show abstract
In this work, admittance loci method is used to model and analyze performance of a chalcogenide prism based plasmonic
biosensor comprising of gold metal nanoparticle film for detection of wavelength dependent refractive index change of
human blood sample under angular interrogation mode. The wavelength dependent performance of the plasmonic
biosensor based on the choice of chalcogenide (2S2G) as a coupling prism material has been discussed with the help of
performance parameter plots.
A self-referencing surface plasmon resonance sensor
Shankar Pidishety
Show abstract
A zero cross sensitivity (CS) deliverable self-referencing (S-R) surface plasmon resonance sensor (SPR) experimental
scheme is presented based on the retroreflecting prism configuration with single spectroscopic read out. The relationship
between external and internal incident angle in retroreflection configuration results in the excitation of two
spectroscopically distinct surface plasmons (SPs) modes corresponding to each side of the prism. The characteristics of
two SPs modes are independent and thus used in differential refractive index (RI) sensing via S-R modes technique. By
applying SR sensing theory, it is shown that the CS can be minimized to zero through the demonstrated configuration.
This configuration is flexible for using in wavelength interrogation measurement method as well. The excited SPs modes
are also tunable to acquire either identical or non-identical sensitivity by selecting corresponding metal film thickness on
the either sides of the prism. From the preliminary experimentation on SR configuration and theoretical investigation on
deliverability of zero CS, it can be expected that the presented scheme is a better SR configuration for high accurate
differential RI sensing applications.
On-line condition assessment of power transformers using wideband FBG based acoustic sensor
Show abstract
Partial Discharges (PDs) are reported as one of the main reason of insulation degradation and its measurement is most
effective, non destructive test often applied to know the insulation condition. Among many available methods acoustic
method of PD test is quite popular due to several advantages.In the presented work, a Fiber Bragg Grating (FBG) based
sensor has been developed for on-line condition assessment, capturing the acoustic wave produced by the PD event in a
prototype power transformer. A variation in acoustic pressure, changes the wavelength of the FBG reflected light, which
gives the indication of PD activity. Developed FBG based sensor is found to be superior over conventional PD sensors.
Spectral analysis of semiconductor-based surface plasmon resonance sensors for infrared-gas sensing
Show abstract
In present analysis a semiconductor-based surface plasmon resonance structure using Gr-IV materials (Silicon and
Germanium) has been analyzed in spectral interrogation mode which can be used for efficient environmental monitoring
and Infrared (IR) gas-sensing purposes. The Silicon-Germanium (Si-Ge) combination structure is able to confine an
extremely high evanescent field in the sensing region due to their extraordinary high refractive indices (RI). Higher
concentration of optical field in the sensing area provides enhanced spectral sensitivity for infrared gas-sensing. Better
detection accuracy and adequate dynamic range are other additional advantages offered by such semiconductor-based
surface plasmon resonance (SPR) configurations. Analysis of the SPR structure has also been carried out in terms of
detection accuracy, figure of merit and Q-factor of the gas-sensor.
Generation of Moiré pattern and its modulation by surface plasmon resonance
Show abstract
Theoretical and experimental investigation of surface plasmon resonance (SPR) assisted radially sheared interference
imaging using a birefringent lens having two longitudinally shifted focal points has been reported. As Wolllaston prism
can introduce lateral shear between the two mutual orthogonal polarizations of radially sheared pattern, Moiré-like
pattern is produced at overlapping region of those patterns. Brief theory and experimental demonstration of coherent and
incoherent Moiré fringe generation has been done. Surface plasmon resonance (SPR) mediated Moiré pattern has been
demonstrated which can be further utilized for other nanophotonic applications.
Titanium nitrides as plasmonic materials in visible frequency range
Show abstract
This paper aims to report simulation based study of performance properties of Titanium Nitrides and their efficient use
as substitutes to metals for excitation and propagation of surface plasmon polariton wave.
Design and proposal of dual line-of-defense perimeter watchdog incorporating optimally designed FBG based accelerometers and strain sensors using single optical fiber
Show abstract
Paper presents Opto-Mechanical intrusion sensor fence with FBGs attached to mechanical accelerometers and strain
sensors, optimized on SolidWorks 2013 for desired frequency to 35 Hz, picking up accelerations/ strains and its
deployment for perimeter security. The accelerometer structure consists of inertial mass supported by an L-shaped
modified cantilever beam having non-uniform cross section area connected to base by a thin neck element which acts as
strain concentrated centre hence an optimum zone for FBG sensors placement. Bragg wavelength shifts were obtained
on Optigrating software for the obtained strain values on mechanical assembly of fence. CFD wind analysis is performed
on the assembly to obtain the spot for accelerometer’s placement to avoid false alarms up to wind velocities of 20 m/s.
Reduction in the amount of crosstalk with reduced number of focal spot rows in a grating array based zonal wavefront sensor
Show abstract
The Shack Hartmann wavefront sensor (SHWS), named after Johannes Franz Hartmann and Roland Shack, is one of the most well-known and popularly used optical wavefront sensor that finds numerous applications in various optical technologies. SHWS samples the incident wavefront by means of a lenslet array to produce an array of regular 2D array of focal spots on the detector plane of a digital camera, in the case of an unaberrated plane wavefront. If the incident wavefront is aberrated or deviates from a plane wavefront, the respective focal spots get shifted from its reference positions corresponding to the regular grid. If the incident wavefront aberration increases or has a very large curvature, the focal spot of one lenslet may enter the detector sub-aperture of the nearby lenslet. Thus, the SHWS has a limited dynamic range that is restricted to aberrations which do not allow the sub-images to be displaced out from their own detector sub-array. It makes the SHWS sensitive to cross-talk when higher order aberrations are present thereby unavoidably a ecting the wavefront estimation process. The array of tiny lenses of the SHWS can be replaced by an array of gratings followed by a focusing lens, generating an array of focal spots which is similar to that as in the case of a SHWS. In this paper, the spatial frequency of such a grating array based zonal wavefront sensor is configured to produce lesser number of rows of focal spots. The reduction in the number of focal spot rows reduces the amount of cross talk in the vertical direction. In this paper we present preliminary experimental results to demonstrate the above stated reduction in crosstalk.
Enhanced sensitivity etched fiber Bragg gratings for precise measurement of refractive index
Show abstract
We demonstrate the use of etched fiber Bragg gratings for sensing refractive index in the range of 1.350-1.453.
Experiments are carried out using FBGs with different etch depths and their relative performances are compared.
Efficient nanoplasmonic antennas for fabricating single protein molecule detector
Show abstract
Real time (label-free) detection and sizing of single protein molecule at its natural state is “holy grail” in biosensing
field. This non-destructive technique is useful for predicting the dangerous diseases at very early-stage. Herein, we
report the synthesis and characterization of efficient nanoplasmonic antennas, which could be useful to fabricate an
ultrasensitive nanoplasmonic-whispering gallery mode hybrid microresonator for the real time detection and sizing of
single protein molecule. This hybrid microresonator could be easily converted as an ultrasensitive single molecule
biosensor by anchoring suitable anti-bodies on the surface of the plasmonic nanoantenna.
Subwavelength plasmonic waveguide coupled nanostub for differential intensity based sensing
Show abstract
We report a transmission line based analysis of a subwavelength nanostub coupled to a metal-dielectric-metal (MDM)
waveguide along with a differential intensity based sensing application related to detection of concentration of glucose in
aqueous solution.
Compact surface plasmonic waveguide component for integrated optical processor
Show abstract
A compact surface plasmonic two mode interference waveguide component having silicon core and silver and GaAsInP
side cladding is proposed for optical processor elements. Coupling operation is obtained by using index modulation of
GaAsInP cladding with applied optical pulse.
Spatially Bessel modulated nonlinear optical similaritons in asymmetric twin-core fibers
Show abstract
We explore the exact optical similaritons of a generalized nonlinear Schrodinger equation(GNLSE) with space-time modulated
dispersion, nonlinearity, external potential and inhomogeneous source. As an application, we study the dynamics of
these similaritons for a spatial Bessel modulated nonlinearity.
Chirped dissipative double-kink and fractional-transform quadratic solitons induced by localized nonlinear gain
Show abstract
We demonstrate that the localized nonlinear gain induces stable chirped dissipative double-kink, fractional-transform,
bell, and kink type solitons in optical mediawith quadratic nonlinearity. To compensate spatially uniform loss in both
fundamental-frequency (FF) and second-harmonic (SH) component of the system, a strongly localized hot-spot, carrying
the nonlinear gain, is added, acting either on FF component or on the SH one.
All-optical binary to Gray code converter and Gray code to binary converter with proper use of nonlinear material
Show abstract
All-optical systems for binary to Gray code conversion and Gray code to binary conversion are proposed where the input
and output binary digits are expressed as the presence (=1) or the absence (=0) of a light signal. The intensity based
optical XOR logic operation is used here to develop the scheme.
Effect of temperature and electric field on quantum cascade laser transients
Show abstract
The dynamics of a quantum cascade laser (QCL) have been analyzed theoretically using a three level rate equation
model. It is observed that the electric field and the temperature affect the QCL turn-on transients significantly.
Giant quintic nonlinearities at slow light level in semiconductor quantum wells
Show abstract
Enhancement of higher order nonlinear susceptibilities are investigated in three level quantum well with a ladder
configuration in the regime of electromagnetically induced transparency. We have identified the existence of giant
third and fifth order nonlinear susceptibilities of the order ~10-22 m4/V4 at pump wavelength of 9.6 μm. The
group velocity is reported to be slowed down by 104 times compared to the speed of light in vacuum.
Comparative photonic bandgap analysis on square and triangular lattice photonic crystal slabs
Show abstract
Photonic bandgap of two dimensional semiconductor photonic crystal structures of square and triangular lattices are
studied using plane wave expansion method. The bandgap and dispersions also studied by introducing point and line
defect in that structure. Hence a comparative study has been presented among the various structures.
Quantum Zeno and anti-Zeno effects in an asymmetric nonlinear optical coupler
Show abstract
Quantum Zeno and anti-Zeno effects in an asymmetric nonlinear optical coupler are studied. The asymmetric nonlinear optical coupler is composed of a linear waveguide (χ (1)) and a nonlinear waveguide (χ(2)) interacting with each other through the evanescent waves. The nonlinear waveguide has quadratic nonlinearity and it operates under second harmonic generation. A completely quantum mechanical description is used to describe the system. The closed form analytic solutions of Heisenberg's equations of motion for the different field modes are obtained using Sen-Mandal perturbative approach. In the coupler, the linear waveguide acts as a probe on the system (nonlinear waveguide). The effect of the presence of the probe (linear waveguide) on the photon statistics of the second harmonic mode of the system is considered as quantum Zeno and anti-Zeno effects. Further, it is also shown that in the stimulated case, it is easy to switch between quantum Zeno and anti-Zeno effects just by controlling the phase of the second harmonic mode of the asymmetric coupler.
Single-frequency continuous-wave tunable ultraviolet sources based on BIBO and PPKTP crystals and their comparative studies
Show abstract
We report on development of tunable, cw, single frequency ultraviolet (UV) source based on intra-cavity frequency
doubling of an optical parametric oscillator (OPO). The singly resonant OPO (SRO) is realized using 25 mm long MgOdoped
periodically poled stoichiometric lithium tantalite (MgO:sPPLT). The SRO, pumped in the green, is intra-cavity
frequency doubled using two different crystals β-BaB2O4 (BIBO) and periodically poled KTiOPO4 (PPKTP) to generate
tunable UV radiation. The BIBO based source produces UV radiation with output power as much as 770 mW at 398.24
nm in elliptic (0.66) spatial beam while pumping at 8W of green power. The UV source can be tuned across 355.2-418
nm with a continuous wavelength tunability of 62.8 nm in single frequency radiation with instantaneous line-width of
14.5 MHz. On the other hand, the PPKTP based UV source generates maximum UV power of 336 mW at 398.28 nm and
wavelength tunability of 18.1 nm in a TEMOO spatial mode with ellipticity of 0.93 for 5W of green pump power. The
line-width of the UV radiation is measured to be 18.5 MHZ. In comparison, PPKTP based UV source provides better
performance than BIBO in terms of beam quality and power stability.
Controlled shaping of photonic nanojets using core shell microspheres
Show abstract
Photonic nanojet (PNJ), the sub wavelength confinement of light by dielectric microspheres is finding applications in
nanoscale imaging, spectroscopy and nano lithography. These applications require control over the length and lateral
dimension of the nanojets. In the paper we present the results of numerical simulation to show that a core shell
microspheres can be used to generate photonic nanojet with controllable length and confinement by varying the
relative refractive index of the microspheres and the separation between the core and shell centers. We show that a
length of up to 27λ can be achieved when the core microsphere has lower refractive index than the shell and lateral
dimensions down to λ/3 with core microsphere having higher refractive index.
Generating multiple narrowband sources from a broadband LED using defects in its top 2D photonic crystal vertical stack
Show abstract
Vertical 2D PhC having a T-type three port channel on top of InGaAs/GaAs broadband IR LED is considered. Top PhC
is created by 2D periodic repetation of InAs rods in air. T-Channel is created by replacing some solid rods by air. Light
from LED is focussed within the channel. Part of LED light having wavelength out side the PhC bandgap will pass
normally and wavelength within PhC will be guided by the channel. By introducing two different defects in the two arms
of ‘T’ channel tuning of two demultiplexed narrowband sources is obtained.
Chromium doped nano-phase separated yttria-alumina-silica glass based optical fiber preform: fabrication and characterization
Show abstract
Transition metal (TM) doping in silica core optical fiber is one of the research area which has been studied for long time
and Chromium (Cr) doping specially attracts a lot of research interest due to their broad emission band covering U, C
and L band with many potential application such as saturable absorber or broadband amplifier etc. This paper present
fabrication of Cr doped nano-phase separated silica fiber within yttria-alumina-silica core glass through conventional
Modified Chemical Vapor Deposition (MCVD) process coupled with solution doping technique along with different
material and optical characterization. For the first time scanning electron microscope (SEM) / energy dispersive X-ray
(EDX) analysis of porous soot sample and final preform has been utilized to investigate incorporation mechanism of Crions
with special emphasis on Cr-species evaporation at different stages of fabrication. We also report that optimized
annealing condition of our fabricated preform exhibited enhanced fluorescence emission and a broad band within 550-
800 nm wavelength region under pumping at 532 nm wavelength due to nano-phase restructuration.
High-power single-mode trench-assisted EDFA
Show abstract
A trench assisted, 0.15-NA, effective single mode leaky Erbium Doped Fiber Amplifier is proposed for high power
applications. The segmented-core of the fiber enables to achieve 783 μm2 mode area which reduces nonlinearity and
increases power handling capacity of the fiber. The leakage loss of the modes is controlled by annular core segments and
low index trench in the cladding. The leakage loss of the LP11 mode is 10.49 dB/m and that of the fundamental mode is
0.017 dB/m at 1530 nm wavelength. We have injected 20 mW power into each mode and have calculated the gain for 26
m length of the fiber using 250 W pump at 980 nm wavelength. The signal power in the LP01 mode is amplified to 122 W
and that in the LP11 mode drops down to 5.78×10-27 W. The low output signal power in LP11 mode ensures selective
single mode amplification of fundamental mode. Selective single mode amplification confirms good beam quality at the
output end.
Traveling wave model of uni-traveling carrier photodiode
Show abstract
A traveling wave time domain model of bulk InGaAs/InP uni-traveling carrier photodiode is presented in
terms of integral carrier density rate equation. The wavelength dependent responsivity at different absorption width
has been derived from quantum mechanical principle. Output photocurrent response with time is found in close
agreement with the experimental value.
Tunable differential polarization phase shifter using electro-optic property of trapezoidal lithium niobate crystal
Show abstract
A mathematical model to study the phase difference introduced between the two orthogonal components of light wave
due to electro-optic effect in a trapezoidal shaped lithium niobate single crystal has been made. Here, the electrodes are
placed on the two opposite non-parallel faces such that the field is nearly perpendicular to the light beam direction. It is
found that for the said geometry of the device structure, the maximum phase difference is a function of oblique angle
between the two non-parallel faces, which has a critical value. Using random optimization technique based on genetic
algorithm, the device parameters can be optimized for any required phase change between the two components of light
wave. The phase difference between the two orthogonal components of light can be made tunable by using a multi-strip
electrode structure. The advantage of this technique is that tunability can be obtained with a constant voltage source.
Condensing polarization mode dispersion using CSRZ-DQPSK modulation in WDM-RoF-PON system
Show abstract
Differential Quadrature Phase Shift Keying (DQPSK) is considered as an acceptable modulation technique for long-haul
high speed communication owing to its ability to diminish the Polarization Mode Dispersion (PMD), non-linear effects
and has constant envelope over the communication. The assessment includes Carrier Suppressed Return to Zero (CSRZ)
modulation format. The combination of CSRZ and DQPSK techniques would result in a high bit rate with better Bit
Error Rate (BER) in Wavelength Division Multiplexing – Passive Optical Network (WDM-PON) setup. The Radio
Frequency (RF) signal is obtained finally for wireless service which can be assessed. . The optical communication
system is expanded by comprising Polarization Multiplexing (PM) which improves the user scope and the spectral
efficiency. The goal is to experimentally analyze the performances of CSRZ-DQPSK modulated non-coherent receiver
for wire and RoF (Radio over Fiber) system for wireless service. Also, equal amount of power is provided for both the
services. The PMD is reduced both the services. The Proposed system can provide flexible, cost-effective and high
bandwidth utilization with reduced BER.
Experimental study of solitonic dispersive wave in photonic crystal fiber
Show abstract
We experimentally observed the emission of phase-matched resonant radiation in the form of solitonic dispersive wave
in a fabricated photonic crystal fiber by pumping picosecond and femtosecond pulses close to zero-dispersion
wavelength in normal dispersion regime. The generation of such phase matched radiation does not require a soliton to be
formed and red-shifted in nature. Shock front from the leading edge of the input pump initiates the resonant radiation.
The radiation develops in the anomalous dispersion domain and found to be confined both in spectral and temporal
domain. The resonance mechanism can be well explained from the numerical simulation governed by generalized
nonlinear Schrödinger equation.
Temperature assisted band-gap engineering in all-solid chalcogenide holey fiber for mid-IR application
Show abstract
Presence of photonic band-gap (PBG) in an all-solid microstructured optical fiber (MOF), made of two fabrication
compatible chalcogenide (Ch) glasses is theoretically investigated for potential application in the functional mid-infrared
(IR) wavelength range. Cross-section of the MOF is formed by assuming periodically arranged wavelength scale circular
air holes in a hexagonal pattern embedded in a uniform matrix. One type of Ch-glass is considered as the background
material whereas another type of Ch-glass is assumed to fill the air holes. The relative index contrast between these two
Ch-glasses is ~ 24%, for which PBG appears only for a suitable range of non-zero longitudinal wave vector. We have
studied the scalability of this PBG by varying the lattice parameter of MOF and optimized the cross-section to attain the
PBG at ~ 2 μm wavelength. Then by utilizing the thermo-optic properties of the glasses, the effect of external
temperature (T) on the PBG is studied, and finally we have proposed a T-tunable wavelength filter/sensor at mid-IR
wavelength with tuning sensitivity as high as ~ 140 pm/°C.
Experimental verification of MMI by singlemode-multimode-singlemode and multimode-singlemode structures
Show abstract
Multimode Interference (MMI) based on self imaging phenomenon is investigated using matrix
approach. Experimentally MMI is verified using singlemode-multimode-singlemode and multimodesinglemode
structures of optical fiber. The results obtained are also verified by BPM technique.
Plasma based optical guiding of an amplitude-modulated electromagnetic beam
Show abstract
We propose the stronger optical guiding of an electromagnetic beam in a plasma by considering the amplitude
modulation of the fundamental beam. With the advent of high power source of electromagnetic radiation, the
electron velocity in a plasma may become quite large (comparable to the light velocity in free space). Thus, the
effect of relativistic mass variation must be taken into account. The relativistic effect of the laser propagation in a
plasma leads to self-focusing because of the dielectric constant of a plasma being an increasing function of the
intensity. The ponderomotive force of the laser beam pushes the electrons out of the region of high intensity, which
reduces the local electron density and increases the plasma dielectric function further, leading to even more selffocusing
of the laser. In this work, we consider a short pulse laser of finite spot size as an amplitude modulation in
time. Our findings show an efficient optical guiding mechanism based on amplitude modulation signal propagation
in plasmas. Medium nonlinearity becomes stronger if an amplitude modulated beam is introduced, which contributes
significantly in laser guiding in plasmas. Furthermore, the rate of laser self-focusing is increased with modulation
index due the fact of stronger Kerr effect. The study related to amplitude modulated optical signal may be useful for
communication technology.
Electromagnetic modes in a parallel plane waveguide filled with nanoparticles
Jetendra Parashar,
Santosh Chauhan
Show abstract
Propagation characteristics of an electromagnetic wave through parallel plane waveguide filled with
nanoparticles is studied. The dispersion relation reveals two modes, a surface plasmon like mode for ω≥ωpe √3 pe ω≤ω , (ω is
electromagnetic wave frequency and ωpe is electron plasma frequency of nanoparticles) and another normal
electromagnetic mode for ω≥ωpe √3 . The plasmon like mode is sensitive to plate separation and the excitation
frequency is higher for smaller plate separation. The cutoff frequency of electromagnetic mode can be varied by
changing the concentration or size of the nanoparticles and also the plate separation.
A RSOA based full-duplex 80 channel CATV signal with 1.25 Gbps data-stream transmission system using optical carrier suppression and injection-locked FPLDs
Show abstract
In this paper a novel architecture has been proposed and developed for full-duplex transmission of 80
channel CATV signal over 80 km single mode fiber (SMF) using various techniques such as mutually injection
locking, optical carrier suppression (OCS) and remodulation etc. The up/downlink transmission performances are
observed by the low bit error rate (BER) values and impressive eye diagrams. The satisfactory values of CNR, CBT
and CSO verify the successful transmission of CATV signals through our proposed configuration.
Full-duplex transmission of FTTX/ethernet services in a RSOA based WDM-PON architecture using polarization multiplexing technique
Show abstract
In this paper a simple architecture has been developed for full-duplex transmission of different services
like Ethernet, FTTX etc through single optical carrier wavelength employing polarization multiplexing technique in
the transmitter end and the user end simultaneously. 10 Gbps and 2.5 Gbps datarates are bidirectionally transported
over 50 km single mode fiber (SMF) to provide Ethernet and FTTX services concurrently to the user. Reflective
semiconductor optical amplifier (RSOA) is used to reuse and remodulate the downlink signal to uplink transmission.
The upstream and the downstream transmission performances are observed by the bit error rate (BER) values and
the eye diagrams obtained by the BER analyzer at both ends.
Fiber interrogator for Bragg grating sensors based on cavity ring-down technique
Show abstract
We report the results of simulations as well as experiments to study the performance of a fiber interrogator based on
cavity ring-down principle.
Design of multistack Fabry-Perot structure with defect as tunable transmission filter for CWDM using FDTD method
Show abstract
The translational symmetry of the periodicity in a photonic crystal can be disturbed by introducing a controlled defect in
its periodicity. The photon localization causes a pass band in the photonic bandgap. Based on this concept, we are proposing
the design of a tunable narrow band filter for multiple wavelengths used for coarse wave length division multiplexing
(CWDM) system. To achieve that, a multiple stack Fabry Perot structure with suitable stack materials and controllable
defect is considered. The proposed Fabry Perot structure consists of periodic layers of electro optic material Lithium
Niobate (nH) and Magnesium Fluoride (nL). The optical length of each such layer is their corresponding quarter wave
length width at the design wavelength λ0 (1.55 μm). The reflection band of the quarter wavelength multilayer structure is
formed due to the periodic repetition of the (LH)NL, where L and H are the quarter wavelength width of the nL and nH
material respectively and N is the number of bilayers. A quarter wave layer L is then inserted between the groups of (LH)N
and (HL)N to form the Fabry Perot resonator structure which can be used for narrow band transmission filter. The
simulation has been carried out in both FDTD and TMM method and compared. As the refractive index of the Lithium
Niobate can be tuned electro-optically, the filter can also be made tunable.
Enhancement of transmission efficiency in a photonic bandgap fiber introducing nonlinearity
Show abstract
This paper introduces the importance of nonlinearity in a Photonic Bandgap (PBG) Fiber using Finite Difference Time
Domain (FDTD) simulation. It is shown that, the amplification of the weaker optical signal in a PBG fiber due to the
constructive interference between two incoming signals can be controlled using nonlinearity.
Parity-time (PT)-symmetric closed-form quadrimer waveguides with focusing and defocusing nonlinearity
Show abstract
In the present work, a PT-symmetric closed-form quadrimer waveguides system has been considered. We observe the
saturation of the optical powers in the gain-guides in nonlinear regime under the coupling scheme considered.
Moreover, we also find that accumulation of optical powers in the g-r parametric space (‘g’ is the gain/loss parameter, ‘r’
nonlinearity co-efficient) in the different waveguides significantly depends on the nature (i.e. focusing or defocusing)
and the strength of nonlinearity and gain/loss profile. The potential applications of this quadrimer system might be in
generating high constant-power optical sources.
Design of optical finite impulse response filter generating arbitrary spectrum output
Show abstract
In the present communication, a procedure for the synthesis of an optical finite impulse response (FIR) birefringent filter
generating arbitrary spectral output is presented. The basic filter consists of a cascaded system of n identical retarders
between two polarizers at the two ends. A mathematical model of the optical FIR filter is introduced using the FIR
theory of digital filter design. The parameters determined by the synthesis procedure are the angles of the optic axes of
the individual crystals and the angle of the output polarizer. Classical FIR filter design method along with the optical
backward transfer technique has been used. Two different arbitrarily specified spectral output profiles have been studied.
However, the method is equally applicable for any periodic transfer function whose corresponding impulse response is
real and causal.
Jones matrix imaging for transparent and anisotropic sample
Show abstract
We propose an experimental technique for two dimensional Jones matrix imaging of transparent and anisotropic sample
using polarization interferometer. Employing this technique, the Jones matrix components are measured for polarizer and
quarter wave plate and results are compared with theoretical results of the samples.
Generalized orbital angular momentum Poincaré sphere
Show abstract
We construct a orbital angular momentum (OAM) Poincar´e sphere in which we can represent 2-D superposition
states of arbitrary OAM. In addition, we represent the mixed states of OAM as non separable states inside the
sphere. We also give an experimental set up to generate all points on this sphere.
Birefringence analysis using Mach Zehnder interferometer
Show abstract
A mathematical model which has been developed for interferometric analysis of birefringent sample is experimentally
verified using a modified Mach – Zehnder arrangement. It is shown that full field analysis of samples with varying
birefringence in magnitude and orientation is possible.
Mueller imaging of blood cells
Show abstract
The polarization parameters of light transmitted through biological cells contain morphological and functional
information for biomedical purposes. As more imaging became available to research applications, Mueller
imaging’s importance has increased regularly in biomedical approach over the years. This paper summarizes
the context of Mueller imaging and polarization optical analysis on blood cells for medical applications.
Basically this method is related to Mueller Matrix Imaging Polarimetry. Knowing all 16-element Mueller
matrix using 36 independent polarization states completely describes the blood cells in terms of birefringence
properties.
Simulation testbed for RF-photonic beamforming networks
Show abstract
A software simulation testbed for measuring the RF characteristics of an Optical Beamforming Network (OBFN), being
designed and simulated in Optical circuit simulator software.
Development of a scalable generic platform for adaptive optics real time control
Show abstract
The main objective of the present project is to explore the viability of an adaptive optics control system based exclusively on Field Programmable Gate Arrays (FPGAs), making strong use of their parallel processing capability. In an Adaptive Optics (AO) system, the generation of the Deformable Mirror (DM) control voltages from the Wavefront Sensor (WFS) measurements is usually through the multiplication of the wavefront slopes with a predetermined reconstructor matrix. The ability to access several hundred hard multipliers and memories concurrently in an FPGA allows performance far beyond that of a modern CPU or GPU for tasks with a well-defined structure such as Adaptive Optics control. The target of the current project is to generate a signal for a real time wavefront correction, from the signals coming from a Wavefront Sensor, wherein the system would be flexible to accommodate all the current Wavefront Sensing techniques and also the different methods which are used for wavefront compensation. The system should also accommodate for different data transmission protocols (like Ethernet, USB, IEEE 1394 etc.) for transmitting data to and from the FPGA device, thus providing a more flexible platform for Adaptive Optics control. Preliminary simulation results for the formulation of the platform, and a design of a fully scalable slope computer is presented.
Conical Fresnel zone lens for optical trapping
Show abstract
The phase of a negative axicon is combined with that of a Fresnel zone lens (FZL) to obtain an element labelled as
conical FZL, which can generate a focused ring pattern at the focal plane of the FZL. The phase integration is achieved
by modifying the location and width of zones of FZL in accordance with the phase variation of the negative axicon. The
element was designed for a high power laser with a wavelength of 1064 nm, focal length and diameter of conical FZL of
30 mm and 8 mm respectively and for a ring diameter of 50 μm. The element was fabricated using photolithography. The
pattern was transferred from the resist layer to the borosilicate glass plates by dry etching to achieve an etch depth of
1064 nm. The etch depth measured using confocal microscope was 1034 nm at the central part and 930 nm for the
outermost part of the device with a maximum error of 12.5% at the outermost part and 3% at the central part. The
element was used in an optical trapping experiment. The ring pattern generated by the conical FZL was reimaged into the
trapping plane using a tightly focusing microscopic objective. Polystyrene beads with diameters of 3 μm were
suspended in deionized distilled water at the trapping plane. The element was found to trap multiple particles in to the
same trap.
Optical transformation based image encryption and data embedding techniques using MATLAB
Show abstract
The proposed work describes optical transformations such as Fourier transformation and Fresnel transformation based
encryption and decryption of images using random phase masks (RPMs). The encrypted images have been embedded in
some secret cover files of other formats like text files, word files, audio files etc to increase the robustness in the security
applications. So, if any one wants to send confidential documents, it will be difficult for the interloper to unhide the
secret information. The whole work has been done in MATLAB®
Contrast-controlled retinal response
Show abstract
A beam of light stimulates the retina weakly when its entry to the pupil is gradually shifted from the centre toward the
edge. For single pupil entrance point the light, irrespective of its coherence would still show the Stiles-Crawford effect
with diminished visibility toward the edge of the pupil. Only when coherent light is incident from opposing points in the
pupil can the effect be cancelled. This paper has attempted a theoretical computation of how the contrast in an
interference pattern formed on the retina controls the retina’s response in three ways; first, by completely disregarding
the Stiles Crawford diminution of effective brightness for unit contrast; next, taking the traditional SCE route for zero
contrast, and finally enhancing the diminution in the effective brightness by giving an opposing boost to the visibility in
commensurate with a contrast intermediate between the two extremes of unity and zero.
Generation of super long dark channel using annular multi-Gaussian beam
Show abstract
According to Vector diffraction theory, focusing properties of azimuthally polarized annular multi Gaussian beam
through dielectric interface is numerically studied. It is observed that the presence of dielectric interface generates focal
shift and the inclusion of annular obstruction at the aperture enhances the focal depth and minimized the focal hole size.
By properly tuning the annular obstruction, a focal hole of FWHM 0.606 λ having super long focal depth of 3080λ is
achieved. The focal depth of the dark channel achieved is found to be much larger than all the previously proposed
methods.
Experimental investigations on implementing different PGC algorithms for interrogation of fiber optic hydrophones
Show abstract
This paper discusses the detailed experimental investigations on the performance of interferometer based fiber optic
hydrophones with different Phase Generated Carrier (PGC) demodulation algorithms for their interrogation. The study
covers the effect on different parametric variations in the PGC implementations by comparison through Signal to Noise
And Distortion (SINAD) and Total Harmonic Distortion (THD) analysis. This paper discusses experiments on most
popular algorithms based on PGC like Arctangent, Differential Cross Multiplication (DCM) and Ameliorated PGC. A
Distributed Feed-Back Fiber Lasers (DFB-FL) based fiber optic hydrophone, with Mach-Zehnder Interferometer having
active phase modulator in reference arm and mechanism to cater polarization related intensity fading were used for the
experiments. Experiments were carried out to study the effects of various parameters like the type and configuration of
low pass filter, frequency of the modulation signal, frequency of acoustic signal etc. It is observed that all the three
factors viz. the type of low pass filter, frequency of modulating and acoustic signal plays important role in retrieving the
acoustic signal, based on the type of algorithms used and are discussed here.
Analysis of OSNR requirements for higher modulation schemes for various local oscillator powers
Show abstract
To meet the growing demands of data traffic in long haul communication, it is necessary to efficiently use the
low-loss region(C-band) of the optical spectrum, by increasing the no. of optical channels and increasing the
bit rate on each channel .But narrow pulses occupy higher spectral bandwidth. To circumvent this problem,
higher order modulation schemes such as QPSK and QAM can be used to modulate the bits, which increases
the spectral efficiency without demanding any extra spectral bandwidth. On the receiver side, to meet a satisfy,
a given BER, the received optical signal requires to have minimum OSNR. In our study in this paper, we
analyses for different modulation schemes, the OSNR required with and without preamplifier. The theoretical
limit of OSNR requirement for a modulation scheme is compared for a given link length by varying the local
oscillator (LO) power. Our analysis shows that as we increase the local oscillator (LO) power, the OSNR
requirement decreases for a given BER. Also a combination of preamplifier and local oscillator (LO) gives the
OSNR closest to theoretical limit.
A novel iris localization algorithm using correlation filtering
Show abstract
Fast and efficient segmentation of iris from the eye images is a primary requirement for robust database independent iris
recognition. In this paper we have presented a new algorithm for computing the inner and outer boundaries of the iris and
locating the pupil centre. Pupil-iris boundary computation is based on correlation filtering approach, whereas iris-sclera
boundary is determined through one dimensional intensity mapping. The proposed approach is computationally less
extensive when compared with the existing algorithms like Hough transform.
Double image encryption using gyrator wavelet transform
Show abstract
In this paper, we implement a novel optical information processing tool termed as gyrator wavelet transform for the
application of double image encryption using amplitude- and phase-truncation approach. This approach enhances the key
space in an asymmetric cryptosystem by adding supplementary security layers, i.e., family of mother wavelet and the
gyrator transform order. Double input images bonded with random phase masks are independently gyrator transformed.
Amplitude truncation of obtained spectrum generates individual and universal keys while phase truncation generates two
real-valued functions. Each of the retrieved amplitude function is discrete wavelet transformed, which results into four
different frequency bands. We have fused the obtained wavelet spectrum of an individual image by again gyrator
transforming them following amplitude- and phase truncation. The obtained real-valued functions corresponding to each
image are bonded to form the encrypted image. After using the correct universal key, individual asymmetric key, type of
wavelet, and correct gyrator transform order, the original images are retrieved successfully. Numerical simulation results
prove that the proposed scheme is more flexible and effective than existing wavelet fusion schemes.
Watermarking in gyrator domain using an asymmetric cryptosystem
Show abstract
A watermarking scheme is proposed based on optical asymmetric cryptography using double random phase encoding in
the gyrator transform domain. It is based on the phase and amplitude truncation during the encryption process. The
scheme is validated through computer simulations showing the scheme's sensitivity to decryption keys and orders of the
gyrator transform. The occlusion and noise attacks have also been analysed. The proposed scheme is significantly
resistant to both these attacks.