Browsing by Author "Fan, JY"

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Laser- and electric-field-induced local refraction index change in a nematic liquid crystal film
(2000-08-01)
Wu, JJ
;
Chen, SH
;
Fan, JY
;
光電工程學系
;
Department of Photonics
We study the Ar+ laser- and electric-field-induced local refraction index change in a planar-parallel-aligned nematic liquid crystal (NLC) film. The laser that is normally incident on the film is strong enough to induce a spatial nonuniformity of the molecular reorientation. The experimental results show that the change of the refraction index of the NLC film is always less than that calculated by the theory in current usage. This is because of the finite beam size effect which is different from the infinite plane wave assumption in the current theory. In this paper, we report some interesting phenomena which result from the finite beam size effect especially near the occurrence of the Fredericksz transition. The experimental results are compared to the theoretical calculations.
Novel diffraction phenomenon with the first order Fredericksz transition in a nematic liquid crystal film
(1998-02-01)
Chen, SH
;
Fan, JY
;
Wu, JJ
;
光電工程學系
;
Department of Photonics
We present the experimental results of the Ar+ laser- and electric-field-induced diffraction effect in a planar-parallel-aligned nematic liquid crystal film. It is found that only one set of diffraction rings occurs in the second order Fredericksz transition; however, two sets of diffraction rings can occur in the first order Fredericksz transition. The appearance of two sets of rings distinguishes the first order Fredericksz transition from the second order. We propose a theoretical explanation for the phenomenon. (C) 1998 American Institute of Physics. [S0021-8979(98)04903-2].