Browsing by Author "Li, WY"

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Electrooptical properties of aligned dye-doped polymer dispersed liquid crystal films
(1998-12-01)
Wu, JJ
;
Wang, CM
;
Li, WY
;
Chen, SH
;
光電工程學系
We investigate how plane-parallel and twisted alignment treatments influence the electrooptical properties of dye-doped polymer dispersed liquid crystal (PDLC) films. These films are transparent in the electric field-on state and opaque in the field-off state. The relationship between field-off state transmittance of such dye-doped PDLC films and polarization of the incident light is discussed. Experimental data confirm that, even for unpolarized : Incident light, the contrast ratio of these aligned films surpasses that of a nonaligned dye-doped PDLC film.
Light scattering from a spherical nematic droplet modulated by an electric field
(1998-06-01)
Chen, SH
;
Li, WY
;
光電工程學系
;
Department of Photonics
We use finite difference and relaxation methods to simulate the three-dimensional molecular director configurations in a spherical nematic droplet in the presence of an electric field. Deformation free energy of the nematic droplet is described in terms of tensor representation. Total scattering cross sections of a single nematic droplet modulated by various electric field strengths are calculated using the anomalous diffraction approach light scattering theory. The electrooptical properties are examined with respect to the droplet size, the dielectric anisotropy and the elastic constants of the nematic liquid crystals.
Simulation of normal anchoring nematic droplets under electrical fields
(1999-03-01)
Li, WY
;
Chen, SH
;
光電工程學系
;
Department of Photonics
In this work we simulate the director configurations of a spherical nematic liquid crystal droplet under normal anchoring conditions to study the changes of the director under varying electric field sequence. The extent to which the orientational properties of the director configurations depend on the dielectric anisotropy and elasticity of liquid is discussed. Simulation results indicate that the bistability of the director configuration causes hysteresis in the transmission-applied voltage properties of a polymer-dispersed liquid crystal film. In addition, lowering the values of dielectric anisotropy to the elastic constant ratio of liquid crystal reduces hysteresis.