Browsing by Author "Hsu, K"

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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.
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.