Long-wavelength infrared transmission filters via two-step subwavelength dielectric gratings

We experimentally demonstrate a long-wavelength infrared narrowband transmission filter using an asymmetric subwavelength dielectric grating. A two-step grating geometry is used to define the asymmetry, which enables resonant narrowband transmission response at normal incidence. Computational modeling is used to show that varying the grating parameter dimensions can shift the transmission peak wavelength. Silicon/air gratings are experimentally demonstrated, with the peak transmission wavelength varying between 10 and 11.3 μm.