Fabrication technique for high-aspect-ratio gratings

摘要

Abstract: High aspect ratio gratings are of interest for a couple of applications. Especially artificial birefringence based on zero order dielectric gratings are calling for small pitches (e.g. $LS 450 nm) and a high aspect ratio (e.g. $GRT 10 in fused silica). One of the most difficult problems is to reach the optical parameters that are demanded. Based on e- beam writing, ion beam etching, reactive ion beam etching and chromium coating we developed a technique for the fabrication of such gratings. In result, we reached phase retardation between TM and TE polarization of more than 90$DGR@. An iterative step technique allows realization of the phase retardation of accuracy better than 1%. The highest aspect ratios of the gratings, we fabricated, were in the range of about 25 at 440 nm period and 100 nm gap.!3