Orientational photorefractive effects observed in polymer-dispersed liquid crystals

We present a novel type of photorefractive polymer-dispersed liquid crystal (PDLC) that contains a polymer, low-molecular liquid crystals (LC's), and a photoconductive sensitizer. Photorefractivity is demonstrated by two-beam-coupling experiments with an external dc field. This material shows highly sensitive photorefractivity, and a purely refractive-index grating $\left(\mathrm{\Delta }n\ge 3.0\times {10}^{-3}\right)$ is generated by irradiation of interference light $\left(\lambda =632.8 \mathrm{nm}\right)$. The grating in the photorefractive PDLC's shows strong anisotropy, and the dynamics depends strongly on the composition. In the case of a $40:60$ weight ratio of polymer:LC's, the photorefractive PDLC's present a stable memory effect.