Omnidirectional and polarization insensitive nearly perfect absorber in one dimensional meta-structure

Abstract

We design and numerically investigate an omnidirectional and polarization insensitive nearly perfect absorber in the mid-infrared regime, which is just a one dimensional metallic grating with a pair of metal–dielectric bilayer on the grating ridge. Absorption peaks of over 99% are simultaneously achieved around the wavelength of 5.73 μm for both TM and TE polarizations, and they also remain very high over a wide range of incident angle for both polarizations. According to the analysis of the electromagnetic field distributions, we attribute the nearly perfect absorption to the magnetic resonances and the cavity modes for the TM and TE polarizations, respectively, which are further confirmed by inductor-capacitor (LC) circuit model and cavity resonance condition, respectively. This simple and flexible one dimensional nearly perfect absorber is particularly desirable for various potential applications including micro-bolometers, band-stop filters and selective thermal emitters.