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 chain. Periodical change in the phase structure was caused reversibly by trans−cis photoisomerization and cis−trans thermal back-isomerization of the azobenzene 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 the grating with a narrow fringe spacing of 1.4 μm was achieved within ∼150 and ∼190 ms, respectively. Moreover, the optical switching behavior of the holographic diffraction was observed repeatedly by turning on and off the writing beams.