79.	Self-organized phase gratings in photoreactive polymer liquid crystals, H. Ono, A. Emoto, N. Kawatsuki and T. Hasegawa, Appl. Phys. Lett. 82 (2003) 1359-1361.

Abstract

Optical phase gratings have been prepared in a photo-cross-linkable polymer liquid crystal substituted with a 4-methoxycinnamoyloxybiphenyl side group by the use of linearly polarized ultraviolet interference light and subsequent annealing. The diffraction was almost invisible after irradiation, and was successfully enhanced during the subsequent annealing. Recorded phase grating involves both linear birefringence and surface-relief modulation, which is generated by thermally enhanced reorientation of the mesogenic groups and molecular migration. The sign of the induced birefringence was dependent on the degree of photoreaction and the reversion of the reorientation direction of mesogenic groups has been observed.