Fabrication of two-dimensional gratings using photosensitive gel films and their characterization

Two-dimensional (2D) surface-relief gratings have been fabricated by the two-beam interference method on photosensitive gel films, which are derived from chemically modified metal-alkoxides, and characterized with respect to surface morphology and antireflection effect. Photosensitive ZrO2 gel film was deposited on a silica glass substrate using the sol that was prepared from Zr-tetrabutoxide chemically modified with benzoylacetone. The gel film was exposed to two-beam interference fringe (1.0 mum period) of He-Cd laser and then rotated by 90degrees in its own plane, followed by an additional exposure. Leaching of the gel film with ethanol gave lattice or island types of 2D-gratings depending on the dose of laser irradiation. The morphology of the gratings changed with irradiation time of laser, leaching conditions and so on. The formation of 2D-grating of island type on a silica glass substrate substantially reduced the reflection at its surface in a wavelength range of 1.3 to 2.6 mum.