Low-Reflection Microstructure Formed by Sol–Gel Process

Abstract

Low-reflection microstructures were formed by the use of a two-beam interference patterning on a photosensitive ZrO2 gel film. Gel films coated on SiO2 glass were exposed to an interference fringe of 325 nm He–Cd laser beams. The substrate was rotated by 90° between the first and second irradiation steps. Island and lattice type periodic two-dimensional structures with a pitch of 1 µm were formed after the irradiation followed by leaching with ethanol. Reflectance of 0.1% for an optically polished SiO2 surface was attained at around a 1750 nm wavelength by the formation of an island-type microstructure. The transmission spectrum was successfully simulated by the rigorous coupled wave analysis. The heat treatment of the microstructure up to a temperature of 200°C was possible in an ambient atmosphere without a conspicuous increase in reflectance.