Holographic image storage in polymer azobenzene liquid crystals

Unique characteristics were observed in phase-type gratings which were formed in polymer liquid crystal (PLC) films. We have investigated the formation and the properties of the holographic gratings recorded in PLCs with azobenzene moieties (photoresponsive unit). Two types of PLCs were examined: homopolymers of azobenzene monomers (PALC) and copolymers with a tolane moiety (mesogenic unit with a high birefringence) in the side chain. The diffraction efficiency (it) was enhanced in the LC phase. We obtained the value of eta of 31% while it was less than 1% in a glassy state in the Raman-Nath regime. This difference may be due to the modulation of refractive index (Deltan) based on alignment change of rnesogens in the PLC film. In addition, we attempted the holographic image storage of three-dimensional (3-D) objects in the PLC film. The 3-D object was reconstructed with high resolution (>5, 000 lines /mm).