Experimental study of liquid-crystal alignment on a surface relief grating

In this experimental work, photofabrication of a surface relief grating (SRG) on poly[(methyl-methacrylate)-co-(DR1 methacrylate)] copolymer was used align liquid-crystal molecules in parallel. The interference pattern of circularly polarized Ar⁺ laser beams was used for this purpose, and the dynamic diffraction efficiency of the grating was measured at the same time. Then, the polymeric layers aligned by SRG were used to fabricate a homogeneous aligned liquid-crystal cell. The SRG-induced optical anisotropy of the empty cell and the cell filled with the well-known 5CB nematic liquid crystal was investigated by polarizing microscopy. In addition, the SRG-induced dichroism was studied by polarized UV-Vis spectrophotometry. Finally, the SRG-induced dichroism and optical anisotropy were compared for four different incidence angles. This alignment technique could have useful applications in in-plane switching LC displays.