Optimization study of metallic hole arrays as the multi-channel spectral filters in long-infrared wavelengths

The development of miniaturized multi-channel infrared filters based on plasmonic metasurfaces is attracting growing attention, driven by its potential applications in infrared imaging, photodetectors, and spectroscopy. However, the advance of such filters in long-infrared wavelengths has rarely been reported. This paper reports our recent progress on developing multi-channel spectral filters based on micrometer metallic hole arrays in the long-infrared band of 10-15 µm. The effects of structural parameters and the shapes of metallic hole arrays on filtering performance are investigated by numerical simulations with the finite-difference time-domain method and then experimentally verified by optical characterizations of fabricated filters using electron beam lithography. The transmission peaks of the filter on a zinc selenide substrate were optimized with a maximum transmittance of 63%. A comparison of the hole shapes shows that elliptical holes give rise to sharper transmission peak quality than round ones by 28%. The progress achieved in this work should be a promising step in the development of metallic hole-based spectral filters with miniaturized dimensions.