| Summary: | 博士 === 國立成功大學 === 物理學系碩博士班 === 92 === Liquid crystals (LCs) have attracted considerable attention owing to the prosperous development of the liquid crystal displays (LCDs). Furthermore, the large birefringence and low switching voltage make LCs to be very suitable for the applications of electro-optical (E-O) devices, such as spatial light modulators, light deflectors and optical shutters.
Among liquid crystal materials, ferroelectric liquid crystals (FLCs) are unique, and of interest to scientists due to their ferroelectrics. They possess very fast response due to their characteristic spontaneous polarization (PS) and a low rotational viscosity. The surface-stabilized FLC mode (SSFLC) has been extensive studied based on such a material, and finds applications for fast E-O devices. Their peculiar director structures, defects formation and dielectric properties also have been studied extensive recently.
This thesis contains mainly two parts. The first part is the studies of a surface stabilized ferroelectric liquid crystal film doped with an azo dye, methyl red (MR). A holographic grating is written in this film, using two coherent Ar+ laser beams. Such a grating is formed by the reorientation of the liquid crystal molecules caused by the interaction with the photo-induced adsorption of the doped azo dyes. Experimental results show that the formed grating is permanent but electrically switchable, with a very low voltage of ~ 0.2 V. The dye-doped SSFLC grating possesses the electrically bistable characteristics of an SSFLC sample.
The second part is the studies of a SSFLC film doped with a small amount of monomer, BAB-6. The alignment performance and electrooptical effect of the SSFLC film polymerized under different polarity of the DC�nfield were examined first. A grating was then fabricated with UV curing of a doped SSFLC cell through a photomask. The formed grating was found to be the mixing of a phase and amplitude grating, and could be switched under applying an appropriate voltage. The response time is in the order of 500 ~ 600 s.
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