Electro-optical switching characteristics of holograms recorded in polymer dispersed liquid crystals

摘要

Electro-optical switching of the diffraction efficiency in volume holograhpic gratings offers the possiblity of real-time control and programmabillity of diffractive optic-cpmonsnets. We have recently demonstrated recording of transmission holographic Bragg gratings in a material system consisting of a phtolointiator dye, coinitiator, a chain extender, a multifunctional acrylate and a low molecular weight nematic liquid crystal. Low voltage scanning electron microscopy studies have shown that the gratings consist of periodic polymer dispersed liquid crystal (PDLC) planes. Electrical switching of a first order Bragg diffracted beam into the zero-order with an applied field of 10V/ #mu# m was observed. Addition of a surfactant to the prepolymer syrup reduces the switching field to approx 5 V/ #mu# m. Fast response times of the order of microseconds were observed for switching and relaxation. We have also demonstrated storage and electrical switiching of holographic image data in PDLC material. The image hologram can be reversibly erased and restored repeatedly by the application of the field (10-15 V/ #mu# m). Switchable reflection gratings were also made in this material system.