Browsing by Author "Shen, YR"

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Interference patterns of scattering light induced by orientational fluctuations in an electric-field-biased nematic liquid-crystal film
(1998-06-15)
Shen, YR
;
Chen, SH
;
Hsu, CH
;
Lai, YC
;
光電工程學系
A new light-scattering phenomenon from a planar aligned nematic liquid-crystal film is observed and studied. This new phenomenon exhibits ring patterns in the orthogonal polarization. A simple model based on optical interference has been developed, and its predictions agree well with experimental observation. (C) 1998 Optical Society of America.
Optical phase conjugation in a nematic liquid-crystal film modulated by a quasi-static electric field
(1997-07-01)
Chen, SH
;
Shen, YR
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A quasi-static field can play an important role in molecular reorientation of the optical nonlinearity in liquid crystals because of the combination of the critical behavior of the sample at the Freedericksz transition and of nonlinear coupling of the optical and quasi-static fields. The nonlinear-optical phenomenon, optical phase conjugation, was observed in an electric-field-biased nematic liquid-crystal film and can be predicted by molecular reorientation calculated with continuum theory. The external field-modulated intensities of the phase-conjugation beams were obtained by both numerical calculation and experimental measurement. At the same time, the rise times of the intensities of phase-conjugation beams were measured for various external fields. (C) 1997 Optical Society of America.
Phase-conjugate reflection and self-starting optical phase-conjugate oscillation in planar nematic liquid-crystal cells
(2003-01-01)
Shen, YR
;
Hsu, HK
;
Chen, SH
;
光電工程學系
;
Department of Photonics
A theoretical model for phase-conjugate reflection of planar nematic liquid-crystal cells is presented based on the continuum theory of liquid crystals and the optical theory of degenerate four-wave mixing. An analytical solution for the phase-conjugate reflectivity R is derived under the undepleted-pump approximation, and the necessary conditions for self-starting optical phase-conjugate oscillation are obtained. The dependence of these conditions on the related physical parameters is also discussed. The reconstruction phenomenon of phase-conjugate light and the self-starting optical phase-conjugate oscillation have been observed experimentally. The intensities of the phase-conjugate light versus the-biased voltages for various incident optical intensities have been measured, and the results agree very well with the prediction of our theoretical model. (C) 2003 Optical Society of America.
Sum-frequency vibrational spectroscopic study of surface glass transition of poly(vinyl alcohol)
(2003-05-06)
Zhang, C
;
Hong, SC
;
Ji, N
;
Wang, YP
;
Wei, KH
Sum-frequency vibrational spectroscopy was employed to study surface glass transition of poly(vinyl alcohol) by monitoring the relaxation of rubbing-induced alignment of surface chains with increase of temperature. The observed chain relaxation is two-dimensional, parallel to the surface. The surface transition temperature is 58 +/- 2 degreesC, essentially the same as the bulk one.