Formation of intensity grating in a polymer liquid crystal with a side-chain azobenzene moiety by photoinduced alignment change of mesogens

We studied the behavior of photoinduced alignment change of a polymer liquid crystal (PLC) containing an azobenzene moiety in the side chain and formation of a grating by means of the photoinduced alignment of PLCs. The alignment change was evaluated by irradiation with s-polarized light at 488 nm. We investigated the effects of light intensity and incident angles of writing beams (two s-polarized (s + s) configuration) on grating formation in PLC films, and explored the relation between the alignment change and diffraction efficiency. The diffraction efficiency showed a maximum when the change in photoinduced alignment was almost complete in the bright area of interference patterns. The maximum value obtained for the modulation of the refractive index was 0.04. These results indicate that a PLC with an azobenzene moiety is effective under (s + s) polarization conditions, compared with other azopolymer systems.