An International Research Journal

AJP

SSN : 0971 - 3093

Vol  15, Nos. 3&4, July-December, 2006

Asian Journal of Physics                                                                                                        Vol. 15, No 3&4 (2006) 199-202


Stokes Interferometry- First Experimental Results


 Vladimir G Denisenkoa ,Vladimir V Slyusara, Marat S Soskina and Isaac Freundb
aInstitute of Physics, National Academy of Science of Ukraine, 46 Prospekt Nauki, Kiev-39, 03650, Ukraine

 bDepartment of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel

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First experimental results are presented for a new form of interferometry based on the use of crosspolarised sample and reference beams and a measurement of the Stokes parameters of the combined beam. This new method is used to obtain a high resolution phase map of a Gaussian laser beam containing an on-axis optical vortex. These initial experimental results are compared with the standard forked fringe interferometric method for measuring optical vortices, and with the theoretical phase map. Excellent agreement is found in all cases, thereby verifying the accuracy of the method. and paving the way for its use in the study of random speckle patterns, as well as in metrologic and other applications.© Anita Publications. All rights reserved.

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References

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Asian Journal of Physics                                                                                                       Vol. 15, No. 3&4 (2006) 203-209


Seidel coefficients in optical testing


1Virendra N. Mahajan*, and 2William H. Swantner,
1The Aerospace Corporation, El Segundo, CA 90245, USA
2Optical Engineering Services, 433 Live Oak Loop NE, Albuquerque NM 87122, USA

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Determination of the Seidel aberration coefficients from Zernike aberration coefficients obtained in optical testing is discussed, and potential pitfalls in the determination process are explained. © Anita Publications. All rights reserved.

Total Refs :12

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Asian Journal of Physics                                                                                                       Vol 15, No. 3&4, (2006) 211-222


A k-space analysis of holographic particle image velocimetry


J M Coupland, N A Halliwell, R D Alcock and C P Garner
Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University,
Ashby Road, Lougborough, Leics. LEI I 3TU

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This paper introduces a new three-dimensional, k-space formulation of scalar wave propagation and describes its use in the analysis of Holographic Particle Image Velocimetry (HPIV). In particular, it is shown that the three-dimensional autocorrelation of scattered fields can be calculated from measurements of the power in the propagating plane wave components. In addition it is shown that this method, which we refer to as Complex Correlation Analysis, is tolerant to phase aberrations introduced by windows or distortions introduced by the holographic recording process. A similar approach is used to analyse the Object Conjugate Reconstruction (OCR) technique to resolve directional ambiguity by introducing an artificial image shift to the reconstructed particle images. An example of how these methods are used together to measure the instantaneous flow fields within a motored Diesel engine is then described. Anita Publications. All rights reserved.

Total Refs: 12

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Asian Journal of Physics                                                                                                       Vol 15, No. 3&4, (2006) 223-231

 

Adaptive reconfigurable optical interconnects


T D Wilkinson, D Gil-Leyva and C Henderson
Cambridge University, Department of Engineering.
Trumpington St, Cambridge CB2 I PZ

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The next generation of applications for liquid crystal over silicon technolgy will be non-display oriented systems such as adaptive optical interconnects, optical switches and optical image processors. We have been developing these new applications both as reconfigurable optical interconnects (or switches) and adaptive optical interconnects. There is a growing need for optically transparent interconnects in both telecommunications networks as well as board to board and chip to chip systems and reconfigurable phase gratings or holograms offer a very exciting solution. Free space optical data transmission is becoming more and more important as the data rate in electronic systems increases into the GHz 7egion in order to avoid data bottlenecks. Past research into free-space optical links has shown that a high level of manufacturing tolerance must be used to maintain the link, however, one way of avoiding these limitation is to use a reconfigurable liquid crystal phase hologram as a beam steering element to compensate for movement between the boards and maintain the optical data path. In this paper we present recent results in utilising phase holograms to steer 5.-ee space optical beams in both a telecommunications switch and a board to board interconnect. © Anita Publications. All rights reserved.

Total Refs: 14

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Asian Journal of Physics                                                                                                       Vol 15, No. 3&4, (2006) 233-242

 

Production and applications of single crystal optical fibres


J H Sharp1, C W P Shi1, I A Watson1 and H C Seat2
1Laser & Optical Systems Engineering Centre, Department of Mechanical Engineering
University of Glasgow, Glasgow G I 2 8QQ, UK
2Laboratoire d 'Electronique, ENS'EEII-IT-LEN7,
2 rue Charles Camichel, BP 7122-31071, Toulouse Cedex 7, France

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Single-crystal fibres combine the material benefits of optical crystals with a waveguiding device geometry. As such they offer potentially significant advantages over conventional optical fibres in some specific fields. However, research in this area has been slow to gather momentum and to fully realise this potential. This paper reviews production methods of single-crystal fibres along with the applications which have been addressed to date along with future application areas. In addition, specific reference is made to the recent work carried out by the authors.

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Asian Journal of Physics                                                                                                       Vol 15, No. 3&4, (2006) 243-251


Fourier domain optical coherence tomography for biological tissue imaging: A Review

 

Zhenhe Ma1, Jingying Jiang2, Qiang Gong1 and Ruikang K Wang1,3

1Institute of Laser and Optoelectronics, Tiajin University, Tianjin 300072, China

2Department of Biomedical Engineering, Tiajin University, Tianjin 300072, China

3Department of Biomedical Engineering, Oregon Health & Science University, Oregon 97006,USA

E mail: wangr@ohsu.edu

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Optical coherence tomography(OCT) is a new imaging modality used to visualize the microstructures beneath tissue surface. It has been demonstrated that this technique provides images with micron resolution in a non-contact and noninvasive way. Traditional OCT is time domain OCT (TDOCT) which is characterized by its reference arm scanning. In recent years, a new approach of OCT based on Fourier domain interferometry is emerged, i.e Fourier domain OCT (FDOCT). FDOCT avoids scanning in the reference arm, thus makes high-speed acquisition possible. This paper reviews the State-of-the-Art of FDOCT. Following a discussion of the basic theory of FDOCT, different set-ups have been presented. Finally, some of the latest progress in FDOCT is listed.© Anita Publications. All rights reserved.

Total Refs: 52

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1 Introduction

                Low-coherence optical interferometry methods, such as time domain OCT [1-8], are capable of providing high resolution, sub-surface depth profiling, and cross-sectional imaging with relatively simple optical arrangements and inexpensive light source. The technique is based on broadband or white-light interferometry. OCT is typically executed in the time domain (TDOCT) by use of a Michelson interferometer in which the optical path length in reference arm is rapidly scanned over a distance corresponding to the imaging depth. The mechanism of scanning largely limits the acquisition speed and makes real-time imaging difficult.

               In recent years, a novel OCT system has been proposed by a number of groups that operates in the frequency domain, i.e. the Fourier domain OCT (FDOCT also called spectral OCT, SOCT) [9-20]. In  FDOCT, a stationary interferometer is used, and the spectrally dispersed out-put of the interferometer ( i.e spectral interferogram) is recorded. The signal returning from the sample arm can be thought of as a superposition of monochromatic waves that interfere with the corresponding components in the reference arm. This interference leads to fringes on the spectrum. Depth information is encoded in the fringe frequencies which can be easily obtained by Fourier transformation of the spectral interferogram. The advantage of FDOCT lies in the fact that the depth information is obtained in parallel. This eliminates the need for reference arm scanning, and increases the stability and simplicity of the instrument. Fast acquisition speed is inherent in the parallel data acquisition. 

               FDOCT has been implemented in free-space optics [21,22] as well as in fiber optics [23,24]. Light sources with central wavelength around 800nm and 1.3μm are normally used in the FDOCT [25]. Some novel devices were introduced into FDOCT system to improve its imaging quality [26,27]. Leitgeb et al  compared performance of TDOCT and FDOCT in 2003  [28]. Currently, the dynamic range of FDOCT can reach as high as 110 dB  [23], and the measuring range upto 6 mm can be achieved. Moreover, with phase shifting method, the measuring range can expand by a factor of 2  [29]. One of the most attracting features of FDOCT is its high speed acquisition.Through high-speed tunable lasers or high-speed line-scan cameras, some groups have realized the axial scan rate up to 15-30 kHz. Currently, FDOCT not only has been used to image transparent tissues, such as eyes [29,30], but also has been applied to measure nontransparent tissues [31].

                This review summarizes the technological advances in Fourier domain OCT that have been made over the last decade. An overview of the technical issues involved in design of the main components of a FDOCT system is presented.

2 Principles of FDOCT

2.1 Basic principles of FDOCT

                FDOCT is based on spectral interferometer where the interference of broadband light waves is registerted by a spectrometer. A partially coherent beam originating from light source is split into two beams. One beam acts as the reference beam and another penetrates the object along the z axis, and is subsequently backscattered from the layers located at different depths (z axis). In other words, this back scattering light from the object consists of many elementary waves emanating from different depths. It is then superimposed with the plane reference wave from the reference beam. At the exit of the interferometer, a spectrometer is used locally to disperse the interference signal that consists of different wavelengths λ within a specified optical band ∆ λ, which is then registered by a linear detector array or CCD camera. The interference signal I(k) (k = 2π/ λ is the wavenumber) can be written as



Asian Journal of Physics                                                                                                       Vol 15, No. 3&4, (2006) 283-293


Counterpropagating beams in photorefractive crystals and
optically induced photonic lattices


M Belie1, M Petrovic2, D Jovic2, A Strinic2, D Arsenovic. S Prvanovic and N Petrovic1
1Texas A & Al University at Qatar P 0 Box 5825, Doha, Qatar
2 Institute of Physics, P 0 Box 57. 11001 Belgrade. Serbia

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A comprehensive numerical study of counterpropagating incoherent beams in isotropic photorefractive crystals and optically induced photonic lattices in such crystals is carried out. A local model with saturable Kerr-like nonlinearity is adopted for the photorefractive media, with an optically generated two-dimensional photonic lattice written within the crystal. Different head-on incident beam structures are considered, such as Gaussians, dipoles, and vortices. We review some of our earlier work and present novel results on the dynamical behavior of counterpropagating beams in a finite hexagonal photonic lattice. © Anita Publications. All rights reserved.

Total Refs : 20

Counterpropagating beams in photorefractive crystals and optically induced photonic lattices.pdf
M Belie, M Petrovic, D Jovic, A Strinic, D Arsenovic. S Prvanovic and N Petrovic

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