ap
ap
An International Peer Reviewed Research Journal
AJP
SSN : 0971 - 3093
Vol 23, No. 4, October, 2014
Asian Journal of
Physics
Vol. 23, No. 4 (2014)
509-515
Digital shear speckle pattern interferometry with holo-elements
R S
Sirohi
Department
of Physics Tezpur University, Tezpur-748 028, India
___________________________________________________________________________________________________________________________________
The paper discusses the theory of digital shear speckle pattern interferometry (DSSPI). DSSPI is used mainly for non-destructive testing but can also be used for quantitative evaluation of strains, slopes and curvatures. Use of holo- and/or diffractive elements due to their multi-function capabilities makes their use in DSSPI attractive. © Anita Publications. All rights reserved.
Total Refs : 12
___________________________________________________________________________________________________________________________________
Asian Journal of
Physics
Vol. 23, No. 4 (2014)
517-526
Real-time amplification of light signals in photorefractive ferroelectric liquid crystals
Takeo
Sasaki, Satoshi Kajikawa, and Yumiko Naka
Department
of Chemistry, Faculty of Science, Tokyo University of
Science,
1-3
Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
___________________________________________________________________________________________________________________________________
The photorefractive effect in ferroelectric liquid crystalline mixtures containingphotoconductive chiral compounds was investigated. Ter-thiophene compounds with chiral structures were chosen as the photoconductive chiral compounds, and they were mixed with an achiral smectic C liquid crystal. The mixtures exhibit the ferroelectric chiral smectic C phase. The photorefractivity of the mixtures was investigated by two-beam coupling experiments. It was found that the ferroelectric liquid crystals containing the photoconductive chiral compound exhibit a large gain coefficient of over 1200 cm-1 and a fast response time of 1 ms. Real-time dynamic amplification of anoptical image signal of over 30 fps using the photorefractive ferroelectric liquid crystal was demonstrated.© Anita Publications. All rights reserved.
Total Refs : 16
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No. 4 (2014) 527-534
Three-dimensional object recognition with joint fractional
Fourier transform
correlator using digital Fresnel holography
Dhirendra
Kumar and Naveen K Nishchal
Department
of Physics, Indian Institute of Technology Patna, Patliputra Colony
Patna 800 013, India
___________________________________________________________________________________________________________________________________
Three-dimensional
(3D) object recognition with joint fractional Fourier transform
correlator is proposed in which the technique of digital Fresnel
holography is used. Digital Fresnel hologram of a 3D object is
synthesized and reconstructed digitally. Performance measure
parameters, such as, discrimination ratio, peak-to-correlation
energy, and peak-to-sidelobe ratio have been computed to check the
strength of the correlation scheme. © Anita Publications. All
rights reserved.
Keywords:
Digital holography; Fresnel diffraction; fractional Fourier
transform; joint transform correlator.
Total
Refs : 29
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No. 4 (2014) 535-542
Compact telephoto objectives with zero Petzval sum using varifocal lenses
Jorge
Ojeda-Castaneda, Cristian M Gómez-Sarabia* and Sergio
Ledesma
Electronics
Department and Digital Arts, Universidad de Guanajuato
Campus
Salamanca, 36885, Guanajuato, México
___________________________________________________________________________________________________________________________________
We present two non-conventionaltelephoto objectives that havezero Petzval sum. These devicesemploytwo or three varifocal lenses, which may be implemented by using a pair of free-form optical elements. Every pair is here denoted as a vortex pair. To our end, we revisit the Gaussian optics of a zoom system having a single varifocal lens. Next, we unveil a telephoto system that uses two varifocal lenses with zero Petzval sum. This system does not require of any axial movement. The optical powers of the varifocal lenses are related by the condition K1 = − K2 = q K0. These lenses are separated by a distance d = 1/QK0; where q and Q are positive real numbers such that 1 ≤ q < Q. We show that this optical system has extremely low telephoto ratios M = 1 – q/Q. Finally, we describe a 3-lens solutionwith zero Petzval sum, which uses three varifocal lenses and it requires anaxial displacement.This latter solution may be useful for reducing other type of aberration rather than field curvature. We discuss what we believe to be the first formulas representing theseimaging devices. © Anita Publications. All rights reserved.
Total Refs : 22
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No. 4 (2014) 543-560
Self-Similarity in the Farfield Diffraction Patterns of Annular Walsh Filters
P Mukherjee
and L N Hazra
Department of
Applied Optics and Photonics, University of Calcutta, Acharya
Prafulla Chandra Shiksha Prangan, JD-2,
Sector-III, Salt Lake, Kolkata 700 098, India
____________________________________________________________________________________________________________________________________
The set of
annular Walsh filters can be classified into distinct self-similar
groups, where members of each group possess self-similar structures
or phase sequences. Annular Walsh filters are derived from the
rotationally symmetric annular Walsh functions which form a
complete set of orthogonal functions that take on values either +1
or –1 over the domain specified by the inner and outer radii of the
annulus. The value of any annular Walsh function is taken as zero
from the centre of the circular aperture to the inner radius of the
annulus. The three values 0, +1 and –1 in an annular Walsh function
can be realized in a corresponding annular Walsh filter by using
transmission values of zero amplitude (i.e. an obscuration), unity
amplitude and zero phase, and unity amplitude and π phase
respectively. Pupil plane filtering by Walsh filters can be used to
tailor the axial and transverse intensity distributions in the
farfield diffraction pattern of these filters. The obscuration
ratio of annular Walsh filters provides another useful degree of
freedom in this venture. Self-similarity has been observed both in
the axial and transverse intensity distribution in the farfield
diffraction pattern of these self-similar annular Walsh filters.
Results of our investigations on the same are reported in this
paper. © Anita Publications. All rights reserved.
OCIS
Codes: (050.1970) Diffractive optics; (050.1940)Diffraction;
(050.1220)Apertures; (100.5090) phase only filters.
Total Refs :
33
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No. 4 (2014) 561-566
Development of a multiaperture imaging system using a microlens array
Unnikrishnan Gopinathan, Amit Agarwal, Amit Aran, Rashmi Negi, Arun Kumar and Ajay Kumar
Photonics Division, Instrument Research & Development Establishment,Raipur Road, Dehradun-248008
___________________________________________________________________________________________________________________________________
Multiaperture imaging systems can achieve performance comparable to single aperture systems with reduced system volume and weight. This paper discusses the design and development of a multiaperture imaging system using Microlens arrays. The shift in the microlenses of the array is used to enhance the resolution of an image produced by a single microlens. © Anita Publications. All rights reserved.
Keywords: Microlens array, Multiaperture imaging
Total Refs : 12
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No. 4 (2014) 567-572
Effect of pump intensity on Two photon induced UV Photoluminescence in PLD thin film of ZnO
Archana Kushwaha, Satchi Kumari and Alika Khare
Laser and Photonics Lab, Department of Physics, Indian Institute of Technology Guwahati
Guwahati -781 039, India
___________________________________________________________________________________________________________________________________
In the present work, high quality transparent ZnO thin film has been deposited on sapphire substrate via pulsed laser deposition (PLD) technique at room temperature. Epitaxial growth of ZnO thin film on sapphire substrate was confirmed by Raman spectrum. The optical band gap was found to be 3.2 eV, which is in accordance with that of single crystal ZnO. A blue shifted two photon induced broad ultraviolet photoluminescenec (UV-PL) having peak at 3.57 eV, was observed via pumping with a 30 mW He-Ne laser at 633 nm. Effect of pump intensity on UV- PL from the ZnO film was studied. The slope of linear fit of the log-log plot of PL intensity vs pump intensity, was found to be ~1.95 confirming the two-photon absorption phenomenon in the film. © Anita Publications. All rights reserved.
Keywords: ZnO thin film, Photoluminscence, Two-photon absorption, excitonic emissions.
Total Refs : 27
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No 4 (2014) 573-579
THz generation in DAST through DFG-Cherenkov phase matching
Nimish
Dixit1, Maria Farooqui2, Ajay
Mishra1, Vijay Kumar2 and Arun Kumar
Gupta1
1Photonics
Research Center, Instruments Research & Development
Establishment (IRDE)
Defence Research & Development Organisation (DRDO), Dehradun-248008, INDIA
2Graphic Era University, Dehradun-248007, INDIA
___________________________________________________________________________________________________________________________________
Numerical simulation has been done to study the Cherenkov difference frequency generation (DFG) in the DAST crystal. Discrete regions of THz frequency in DAST have been identified to study the tuning characteristics. A maximum of 9.4 MW Cherenkov DFG power was obtained at 0.82 THz corresponding to which the Cherenkov angle was 32.76°. We have also simulated the spatial field distribution for 0.82 THz in DAST crystal, which clearly exhibits the wedged- shape phase fronts of THz radiation. The tuning characteristic of Cherenkov DFG has been compared with that of collinear DFG. A maximum of 2.6 W of collinear DFG power was obtained at 0.48 THz while at the same frequency the Cherenkov DFG power was found to be 5.17 MW. The variation of Cherenkov DFG power with the input beam spot size has also been investigated. It was found that Cherenkov phase matching was almost twice more sensitive towards spots size variation as compared to collinear phase matching. © Anita Publications. All rights reserved.
Keywords: Cherenkov phase matching, collinear phase matching, difference frequency generation, DAST.
Total Refs : 9
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No 4 (2014) 581-590
Characterization of multichannel deformable mirror for adaptive optics applications
Awakash Dixit1, 2,Vikash Porwal1 and Sanjay Kumar Mishra1
1Adaptive
Optics Division, Instruments Research & Development
Establishment (IRDE)
Defence Research & Development Organisation (DRDO),
Dehradun-248008, INDIA
2Uttarakhand Technical University, Dehradun-248007,
INDIA
___________________________________________________________________________________________________________________________________
Deformable mirror is used for correcting the aberrations of an optical wavefront in adaptive optics. In this paper, 97 channel deformable mirror having PZT actuation mechanism is characterized and results are presented. Performance of deformable mirror depends on the various parameters such as initial mirror surface figure, single actuator stroke, inter-actuator stroke, inter-actuator coupling and mirror response functions. These parameters are measured experimentally using an Interferometer and a Shack-Hartmann wavefront sensor. Results are discussed by analyzing the interferograms of the deformable mirror surface and phase data from the Shack-Hartmann wavefront sensor for various cases. © Anita Publications. All rights reserved.
Keywords: Adaptive optics, Deformable mirror, Shack-Hartmann wavefront sensor.
Total Refs : 35
____________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No 4 (2014) 591-596
Design of long period waveguide grating filters using genetic algorithm optimization
Girish Semwaland Vipul Rastogi
1Instrument Research and Development Establishment Dehradun-248008, India
2Indian Institute of Technology Roorkee, Roorkee-247667, India
___________________________________________________________________________________________________________________________________
Global optimization properties of genetic algorithms (GA) have been utilized to design long period waveguide grating devices for the application specific spectra. Pre-defined target spectra corresponding to specific application have been considered. The grating parameters of corrugated grating have been obtained using GA optimization to achieve these target spectra. The simulation results show that the method is easy to implement and useful to design the grating for any pre-defined application specific spectra. © Anita Publications. All rights reserved.
Total Refs : 14
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No 4 (2014) 597-612
A cryptosystem for watermarking based on fractional Fourier transform using a random phase mask in the input plane and a structured phase mask in the frequency plane
Hukum Singh*, A K Yadav, Sunanda Vashisth, and Kehar Singh
Department of Applied Science
ITM University, Sector 23-A, Gurgaon-122 017, India
___________________________________________________________________________________________________________________________________
A watermarking scheme has been proposed in the fractional Fourier transform (FrFT) domain, using a random phase mask in the input plane and a phase mask based on the devil’s vortex Fresnel lens (DVFL) in the frequency plane. The use of a structured phase mask based on the DVFL provides an advantage of extra encryption parameters, besides overcoming the problem of axis alignment associated with an optical set-up. The encrypted image resulting from the application of FrFT is attenuated by a factor and combined with a host image to provide a watermarked image. The decryption process is the reverse of the encryption. Digital implementation of the proposed scheme has been performed using MATLAB 7.1. The validity of the proposed scheme has been established by comparing the results of decryption with the input images. The performance of the scheme has been evaluated in terms of mean-squared-error (MSE). In addition, the sensitivity to encryption keys such as DVFL parameters and the FrFT orders has been studied. The proposed technique provides enhanced security. © Anita Publications. All rights reserved.
Keywords: Fractional Fourier transform, watermarking, devil’s vortex Fresnel lens, mean-squared-error, peak-to-signal-noise ratio.
Total Refs : 64
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No 4 (2014) 613-622
Periodically poled lithium niobate for Mid-IR tunable wavelength
generation using
nonlinear frequency downconversion
Ajay Mishra,
Nimish Dixit, O P Naraniya, B P Dimri and Ajay Kumar
Photonics
Research Center, Instruments R & D Establishment
Dehradun – 248 008, India
___________________________________________________________________________________________________________________________________
In the present work, we demonstrate a high repetition rate mid-infrared tunable wavelength generation in a singly resonant Optical Parametric Oscillator (OPO). A multi-grating periodically poled LiNbO3 (PPLN) fabricated in our laboratory has been used as a nonlinear converter. Multi-grating PPLN chip, which has been fabricated using electric field (E-field) poling technique, contained gratings with varying periodicity from 25.0 to 32.0 µm in the steps of 0.5 µm. The gratings have been observed to have around 45% duty cycle that is required for efficient parametric conversion. This period variation corresponds to the generation of signal beam from 1.3 to 1.9 µm and Idler beam from 2.4 to 4.8 µm, respectively for 1064 nm pump beam. A 1064 nm Q-switched Nd:YVO4 laser at 10 KHz repetition rate and pulse width of 18.7 ns was used to pump the OPO. A maximum of 200 mW signal power and 150 mW of Idler power have been obtained with an input pump beam of power 2.6 W, for a period of 29.5 µm. A maximum optic-optic conversion efficiency of 14 % and 6 % in the idler has been observed. It has been observed that as we increase the period of the grating output power increases.© Anita Publications. All rights reserved.
PACS: 42.65.Ky, 42.65.Lm, 42.65.Yj, 42.65.Mp
Keywords: Optical Parametric Oscillator, PPLN, Parametric Generation, Frequency down conversion
Total Refs : 22
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No 4 (2014) 623-626
Core technology for Terahertz
applications
Surya P
Tewari
Formerly
at Advanced Centre of Research in High Energy Materials and School
of Physics
University of Hyderabad, Hyderabad, Andhra Pradesh
___________________________________________________________________________________________________________________________________
The terahertz (1012 Hz) frequency range generation in condensed matter by asymptotic approaches from microwave side and from optics side needs to give way to the core Technology, which requires small device with low input power for the development and use of THz science for evolving technologies, which will take process monitoring and biological researches to high level of sophistication. © Anita Publications. All rights reserved.
Keywords: Terahertz, Harmonic oscillator/s, nonlinear interactions
Total Refs : 7
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No 4 (2014) 627-630
Wave propagation in ternary photonic
crystal with metamaterials
Laxmi Shiveshwari
Department of Physics, K. B. Women’s College, Hazaribag 825 301, India.
___________________________________________________________________________________________________________________________________
The photonic band structure of one dimensional ternary photonic crystal made of a conventional dielectric material, a negative permittivity and a negative permeability metamaterial is studied theoretically using the transfer matrix method. The proposed structure eliminates the Brewster’s angle transmission resonance giving a complete photonic band gap, completely independent of polarization dependent weakly on angle of incidence.© Anita Publications. All rights reserved.
Keywords: Metamaterial, Complete band gap, Photonic crystals.
Total Refs : 10
___________________________________________________________________________________________________________________________________
Asian Journal of Physics Vol. 23, No 4 (2014) 631-640
Thermally actuated MEMS micromirror: Design Aspects
V Merea, b, Vikram Maharshia, Aditia, b and Ajay Agarwala, b
aCSIR- Central Electronics Engineering Research Institute (CSImR-CEERI), Pilani-33303, India
bAcademy of Scientific and Innovative Research (AcSIR), New Delhi, India
___________________________________________________________________________________________________________________________________
The paper presents thermally actuated micro-mirrors with three degrees of freedom. The bimorph actuators are made of aluminum and silicon. The mirror and actuators are connected and thermally isolated through meander springs. Heaters with aluminum as the heater element were optimized using COMSOL simulation. The maximum actuator deflection is achieved at heater temperature of 106.59°C at applied voltage 0.2 V, with a response time of 0.9 ms. The resulting tilt angle of the mirror is ±4.73 degrees. In piston mode the mirror displacement of 30 mm is achieved for the same applied voltage.© Anita Publications. All rights reserved.
© ANITA PUBLICATIONS
All rights reserved
Designed & Maintained by
Manoj
Kumar