Dual-channel Ultra-narrowband Mid-Infrared Filter Based on Bilayer Metallic Grating

Abstract Traditional dual-channel ultra-narrowband filters are mainly fabricated by multilayered thin films in accordance with interference effect, with the multilayered film structure being so thick that the environment adapatability can not be guaranteed as a problem especially for the infrared dual-band-pass filter which is as thick as ten times of micrometers. Based on this problem, we designed an ultra-thin dual-channel mid-infrared ultra-narrowband filter with fewer layers and bilayer metallic gratings here by integrating the interference effect with Fabry-Perot-like cavity resonance effect, of which the filter has a thickness of 5 um, one third of the tranditional ones, and the minimum half bandwidth is only 0.015 nm. The results reported provide a new approach for designing ultra-thin dual-channel mid-infrared ultra-narrowband filters.