Dynamic studies of holographic gratings in dye-doped liquid-crystal films

The dynamic behavior of a holographic grating induced in a homeotropically aligned dye-doped liquid-crystal film is investigated. In the presence of a n applied dc voltage, photoexcited azo dyes induce a photorefractive gratin g and then diffuse and are adsorbed onto cell substrates. The reorientation of liquid crystals as a result of adsorbed dyes leads to a phase grating t hat is phase shifted 90 degrees from the photorefractive grating. Competiti on of these two gratings induces two-beam coupling of the writing beams, in itially transferring energy from beam I to beam 2 and then, after a pause, from beam 2 to beam 1. (C) 2001 Optical Society of America.