Browsing by Author "Hsieh, TC"

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One-dimensional self-focusing in photorefractive Bi12SiO20 crystal: theoretical modeling and experimental demonstration
(1999-04-15)
Tsai, J
;
Chiou, A
;
Hsieh, TC
;
Hsu, K
;
電子物理學系
We have experimentally demonstrated one-dimensional self-focusing of a laser beam in a photorefractive Bi12SiO20 (BSO) crystal with an externally applied DC field. Fractional change in focal length larger than 50% was measured when the biased field was varied from 2 kV/cm to 8 kV/cm. Based on the band transport model, thin crystal approximation, and gradient index (GRIN) lens approximation, we derive a mathematical expression that describes the effect quantitatively. (C) 1999 Elsevier Science B.V. All rights reserved.
Optical image recognition using photorefractive crystal plates
(1997)
Hsieh, ML
;
Lin, SH
;
Hsu, KY
;
Hsieh, TC
;
Lin, SP
We demonstrate a real-time optical image recognition system using photorefractive thin plates. The effects of donor/acceptor concentration ratio in thin lithium niobate crystal plates on the photorefractive response time and the grating diffraction efficiency are presented.
Optimal conditions for thermal fixing of volume holograms in Fe : LiNbO3 crystals
(1999-10-10)
Hsieh, CR
;
Lin, SH
;
Hsu, KY
;
Hsieh, TC
;
Chiou, A
We analyze and compare two typical recording and thermal fixing procedures of a volume hologram in a Fe:LiNbO3 crystal (low-high-low procedure and high-low procedure). We consider the kinetics of the recording, compensating, and developing processes by taking into account the ratio of the conductivities between the protons and the electrons as a function of temperature. From the analysis the optimal environmental conditions tin terms of the fixing temperature and the compensation time) for each fixing procedure can be deduced for a crystal with given material parameters. (C) 1999 Optical Society of America.
Optimum conditions for thermal fixing of volume holograms in Fe : LiNbO3
(1999)
Lin, SAH
;
Hsieh, CR
;
Hsieh, TC
;
Hsu, KY
;
光電工程學系
The kinetics of the recording, compensating, and developing processes in two typical thermal fixing procedures (L-H-L and H-L procedures) are analyzed. The optimum condition (in terms of the fixing temperature, compensation time and material parameters) for each fixing procedures are obtained under the boundary condition of short-circuit. Experimental results are shown which are in qualitative agreement with the theory in L-H-L procedure.
Photorefractive Fe : LiNbO3 crystal thin plates for optical information processing
(1999-07-01)
Lin, SH
;
Hsieh, ML
;
Hsu, KY
;
Hsieh, TC
;
Lin, SP
The effects of the donor acceptor concentration ratio in iron-doped Lithium niobate (Fe:LiNbO3) crystal plates on photorefractive response time and on grating diffraction efficiency are studied both theoretically and experimentally. The results provide a useful guide for designing photorefractive plates far optical information-processing applications. Two devices for real-time image recognition have been demonstrated: a photorefractive joint-transform correlator and a VanderLugt correlator. The former emphasizes fast response time, and the latter emphasizes high diffraction efficiency. By appropriate adjustment of the dopant concentration and the ratio of the donor acceptor levels, photorefractive Fe:LiNbO3 crystals that facilitate specific applications have been designed and fabricated. Shift-invariant image correlations have been achieved. (C) 1999 Optical Society of America [S0740-3224(99)01307-7].
The self-defocusing of a diffraction beam in a photorefractive crystal and its application in a Fourier plane multiple beam splitter
(1999-09-15)
Tsai, J
;
Chiou, A
;
Hsieh, TC
;
Hsu, K
;
電子物理學系
We propose using a diffraction beam to induce a self-defocusing lens and applying it in a Fourier plane multiple beam splitter (FPMBS). The self-induced lens array in the FPMBS can increase the splitting ratio, which is generated by inserting a photorefractive crystal at the Rayleigh distance of the diffraction beam from each pixel. (C) 1999 Elsevier Science B.V. All rights reserved.
The spatially-distributed recording of the composite filter using the pixelated liquid crystal display
(1999-05-15)
Tsai, J
;
Lin, SH
;
Hsieh, TC
;
Hsu, K
;
電子物理學系
A new recording method using a liquid crystal display (LCD) as an input device to synthesize a composite filter is presented. The filter in the optical correlator makes use of the multiple diffraction orders from the pixelated structure of the LCD panel. During the recording stage, each training pattern is sequentially recorded as a sub-filter at different diffracted order by holographic technology. After that, an input pattern could be simultaneously processed with all sub-filters in parallel such that the composite filter can be achieved. This recording method with spatial distribution could avoid the low efficiency of the conventional multi-exposure. The simulations and experimental results show that this system can perform invariant correlation as a composite filter. (C) 1999 Published by Elsevier Science B.V. All rights reserved.