Polarization controllable Fresnel lens using dye-doped liquid crystals

A scattering-free, polarization controllable Fresnel zone plate lens is demonstrated using a photo-induced alignment of the dye-doped liquid crystal film. This photo-aligned liquid crystal zone plate provides orthogonal polarization states for odd and even zones. The different focus orders can be separated because of their different polarization states. The fabrication process is relatively simple and the operation voltage is less than 5 V-rms

Degenerate Four-Wave Mixing Process and Switchable Grating/Hologram Formation in Polymer-Dispersed Liquid Crystal Films

[[abstract]]We have developed an economic liquid crystal-polymer dispersion material that can be used for optically storing holographic images. Using the thin films of this material, we have observed a strong degenerate four-wave mixing (DFWM) effect during the writing of a grating when the writing beams have intensities above a threshold. Both the threshold intensity and the gratings� diffraction efficiency were measured as a function of the grating constant. The results are reported

Raman Studies of Polymer-Dispersed Liquid Crystal Films

[[abstract]]We have performed the Raman experiments on polymer-dispersed liquid crystal (PDLC) films made from E7-EP0305 mixtures cured at various temperatures. The results show that, both the low frequency field applied to the sample and the liquid crystal droplet size affect the Raman intensities significantly. A simple theory that can be used to explain these results is given

Polymer-dispersed Liquid Crystal Films for Storing Optical Holographic Images

[[abstract]]We have developed an economic liquid crystal-polymer dispersion material that can be used for storing optical holographic images. In this paper, we demonstrate the use of thin samples of this material for such an application. The obtained results show that the written gratings-holograms are permanent, but are electrically switchable. Furthermore, the diffraction efficiency is high and does not change significantly after many tests over a period of months. Thus, we believe this material is promising for practical uses

Dynamical Studies of Gratings Formed in Polymer-dispersed Liquid Crystal Films

[[abstract]]The use of polymer-dispersed liquid crystal films to fabricate gratings was demonstrated. The written gratings are permanent, but are electrically switchable. In this article, we report the results obtained from the dynamical studies of gratings formed in polymer-dispersed liquid crystal films having various liquid crystal-polymer mixing ratios. The results showed that during the initial phases of formation, a thermal grating effect dominated. Later, it was offset or quenched by the photopolymerization effect which eventually dominated and determined the characteristics of the final grating

Studies of Polymer-Stabilized Cholesteric Liquid Crystal Texture Films

[[abstract]]Cells of polymer-stabilized cholesteric texture (PSCT) were fabricated with various polymer concentrations. The structure of the polymer network and the electro-optical characteristics of the devices were studied. The result clearly demonstrates the polymer stabilization effect on the liquid crystal domains in the cells. In addition, the hysteresis characteristics and the dielectric properties of the cells were studied as a function of the driving frequency. The results lead to the conclusion that the polymer enhanced hysteresis effect in PSCT cells is mainly caused by the aligning effect of the polymer network

Photo-patterning micro-mirror devices using azo dye-doped cholesteric liquid crystals

A simple method for fabricating patternable micro-mirror devices by photo-induced alignment of dye-doped cholesteric liquid crystal (CLC) is demonstrated. The CLC texture can be changed from random distribution to nearly perfect planar by the photo-excited adsorbed dyes. This structure transformation leads to a substantial reflectivity increase. Using this photo-patterning technique, one- and two-dimensional micro-mirror arrays which function as gratings are also demonstrated