Direction-independent dual-band perfect absorption induced by fundamental magnetic polaritons

In this paper, we designed a single sized Metal-Insulator Pair-Metal hybrid grating for dual-band perfect absorption from 8 μm to 14 μm utilizing both nondispersive insulators and dispersive phonic insulators. The hybrid grating was composed of Al/ZnTe-SiC pair/Al, which incorporated an ultrathin phononic SiC layer between the nondispersive ZnTe dielectric spacer and Al substrate. The physical mechanisms responsible for the dual-band perfect absorption were elucidated by the resonance of fundamental magnetic polaritons (MPs). Dual-band perfect absorption with incident angle insensitive feature was enabled. An equivalent LC circuit model predicting the dual-band resonant absorption peaks wavelengths was proposed and verified. Furthermore, the effects of grating period, strip width, nondispersive dielectric spacer thickness and polar phononic dielectric spacer thickness on the absorption were explored.