Control of Thermally Enhanced Photoinduced Reorientation Direction of Photocrosslinkable Copolymer Liquid Crystals and Application to Polarization Gratings Using Linearly Polarized Ultraviolet Light

In this paper, we describe the thermally enhanced photoinduced reorientation behavior of copolymer liquid crystals, which comprise a methacrylate with 4-(4-methoxycinnamoyloxy)biphenyl (MCB) side groups and N-phenylmaleimide (PM), by irradiating with linearly polarized ultraviolet (LPUV) light and subsequent annealing. Adjusting the exposure energy controls the reorientation direction both perpendicular and parallel to the polarization of LPUV light. The generated birefringence is greater than 0.19 for both directions. A polarization grating with molecular orientation periodically modulated in orthogonal directions is fabricated using a grating photomask. The changes in the polarization of diffracted beams are similar to those of a polarization grating fabricated by a holographic technique.