Caroline Novak with Kenneth Singer
Photorefractive properties of liquid crystal-filled bacterial cellulose mats
The photorefractive effect is a phenomenon associated with nonlinear optical materials in which the refractive index of the material varies with the application of light. One demonstration of this effect is dynamic holography. Energy transfer between diffracted beams can be used, for example, to determine the properties of the sample under investigation, such as the coupling coefficient. It has been found that the strong photorefractive effect in liquid crystal cells arises from photoinduced surface charge modulation on the transparent conducting surface. This limits the photorefractive holograms to the thin film regime, which is of limited use for dynamic holography applications. Bacterial cellulose (BC) mats, made easily by fermentation, can provide a complex nanoscale network of cellulose fibers that can be infiltrated with liquid crystals. Properly treated fiber surfaces could provide a dense network of photosensitive surfaces that would permit the generation of thick film gratings for dynamic holography, while providing for the robust photorefractive response of liquid crystals. In this project, I use dynamic holography techniques to explore the photorefraction of nematic liquid crystal-infiltrated BC mats.