Photoconductive polymer-liquid crystal systems for efficient beam control and amplification

We report on reorientation and two-beam coupling process in liquid crystal cells with different aligning polymer layers. Polymers such as poly(N-vinyl carbazole), pure and doped with fullerenes as well as standard polyimide layers were considered. Electric field distribution inside a liquid crystal cell was modelled and different penetration depths into the liquid crystal bulk were calculated depending on the modulation of surface electric field. The characteristics features of reorientation process were studied via measurements of capacitance with an increasing DC field. The evidence of strong screening was found in cells with photoconducting polymers, as well as in those with thicker polyimide layers. Surface screening layers could be discharged by illuminating a cell with light to induce selective reorientation of a liquid crystal director