Novel direction selective filter elements based on high-contrast gratings
We introduce concepts for direction selective transmission filters based on dielectric high-contrast gratings. The devices act as angular bandpass filters at an incidence angle of 45° with a total transmission of 68% and a full width at half maximum of 20°. Since the filters are based on a material combination of silicon and silicon dioxide they provide an excellent compatibility to well established fabrication processes in semiconductor industry. The results of measurements on fabricated samples are presented and the performance of the components is compared to that of metallic gratings. It is found that the latter can basically provide similar filter properties, however the feasible transmission efficiency is significantly lower than for the dielectric gratings. The presented configurations are applicable in the field of sensors and detectors.