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

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.