ELECTROOPTICAL SWITCHING CHARACTERISTICS OF VOLUME HOLOGRAMS IN POLYMER-DISPERSED LIQUID-CRYSTALS

Electrically switchable volume holograms lead to the possibility of re al-time electrooptical control of diffractive optic components. We rep ort here on the development of a novel photopolymer-liquid crystal com posite material system for writing in a fast single step, high diffrac tion efficiency volume holograms, capable of switching in applied elec tric fields of low voltage. Switching of a first-order Bragg diffracte d beam into the zero-order with an applied field of similar to 10 V/mu m was observed. With the addition of a surfactant to our pre-polymer syrup, we observed lowering of the switching fields to similar to 5 V/ mu m. We report response times for switching and relaxation in the ord er of microseconds. Low voltage, high resolution scanning electron mic roscopy studies show that the Bragg gratings formed consist of periodi c polymer dispersed liquid crystal planes. The addition of surfactant leads to formation of very uniform small (20-40 nm) nematic droplets. A simple model based on the shape of the liquid crystal droplets was a pplied to explain the switching fields and response times.