Fabrication of polarization grating and surface relief grating in crosslinked and non-crosslinking azopolymer by polarization holography method

Abstract

Pure polarization grating without surface topology on crosslinked azopolymer film was fabricated upon exposure to an interference pattern of orthogonal linearly polarized beams from a He–Cd laser without any subsequent processing steps. The grating structure was investigated using atomic force microscopy and polarization optical microscopy. A regular spaced grating but without surface relief was observed. The grating was stable at ambient conditions and can endure repeated writing–erasing processes. The interference mode of writing beam had a significant effect on grating formation and was investigated by using the two patterns of orthogonal linearly polarized beams (polarization-modulated mode) and parallel linearly polarization beams (intensity-modulated mode). The effect of material crosslinking was also studied by comparing the surface relief depth on the grating formation process between crosslinked and non-crosslinking azopolymer films. Experiment results demonstrated that the surface relief grating was observed on non-crosslinking azopolymer film. For intensity-modulated interference mode, whatever crosslinked and non-crosslinking azopolymer films, the surface relief gratings were fabricated.