Photochemically induced dynamic grating by means of side chain polymer liquid crystals

Dynamic holographic grating by means of photochemical nematic-to-isotropic phase transition has been studied in a polymer liquid crystal containing an azobenzene moiety with strong donor-acceptor substituents in the side chai n. Periodical change in the phase structure was caused reversibly by trans- cis photoisomerization and cis-trans thermal back-isomerization of the azob enzene moiety and led to formation of the dynamic grating following change in refractive index on the order of 10(-2). The production and removal of t he grating with a narrow fringe spacing of 1.4 mu m was achieved within sim ilar to 150 and similar to 190 ms, respectively. Moreover, the optical swit ching behavior of the holographic diffraction was observed repeatedly by tu rning on and off the writing beams.