Fabrication and Characterization of Diffraction Gratings Using Photosensitive Al2O3 Gel Films

A new process for the fabrication of diffraction gratings has been proposed using photosensitive Al2O3 gel films in combination with a phase mask. Photosensitive Al2O3 gel films were derived from Al(O-sec-Bu)3 chemically modified with benzoylacetone. These gel films exhibited an optical absorption band in the UV-range, which is associated with the π–π* transition of chelate rings of the β-diketonate ligand. The irradiation of these gel films with XeF and KrF excimer lasers decreased their solubility in acetone containing 1.2 vol%HNO3, simultaneously with the dissociation of the remaining chelate rings. The above findings were applied to the fabrication of Al2O3 film diffraction gratings on Si and silica substrates; the gel films were irradiated with the excimer lasers through a phase mask, leached, and then heat-treated. The diffraction efficiency of the fabricated gratings was evaluated in reflection (Si sub.) and transmission (silica sub.) modes with respect to the preparation conditions.