Mark Winkler with Ken Singer

Surface Mediated Photorefraction in Liquid Crystals

Liquid crystals are known to have interesting photorefractive properties.  One way to induce a large photorefractive effect is to layer a liquid crystal and a photoconductor.  Light-induced modulation of surface charge on the photoconducting layer lowers the surface energy of the liquid crystal, inducing molecular reorientation (and thus photorefraction) in the bulk of the material.  In this project, we will attempt to intensify the observed photorefractive effect in the liquid crystal 5CB by increasing the surface charge on the photoconducting layer, using ionic polymers to increase the surface charge and gold nanoparticles to increase photoinduced charge generation through amplification of the internal electric field.  Techniques will include dynamic holography, 4-wave mixing, and surface charge generation on a photoconductor.