Holographic gratings and holographic image storage via photochemical phase transitions of polymer azobenzene liquid-crystal films

Phase-type gratings formed by photochemical phase transitions of a polymer azobenzene liquid crystal have been characterized. The sensitivity of the material was improved by a factor of 23 in the liquid-crystalline phase owing to effective induction of the photochemical phase transition in the bright fringes of the interference pattern. A mechanism for grating formation in films based on dynamics both in grating formation and for the photochemical phase transition has been proposed. Observation of the grating structure with a polarizing optical microscope confirmed that the isotropic phase induced photochemically was arranged at well defined separations. The polymer azobenzene liquid crystal showed a storage capability of >100 Mbits cm−2 which corresponds to a resolution of <1 µm and a spatial frequency of >1000 lines mm−1. We also attempted holographic image storage using a photomask as an object.