Stacked all-dielectric absorber based on degenerate critical coupling for visible to near-infrared light

Abstract

We design a wideband all-dielectric perfect absorber of nanopillar Mie resonators based on degenerate critical coupling. In addition, the nanopillar perfect absorber is found to have a characteristic “degenerate critical length” beyond which the absorption peak is almost unaffected by increasing length. Based on the existence of the degenerate critical length, we develop a broadband dielectric quasi-perfect absorber by stacking nanopillar Mie resonators of different materials that selectively absorb incident light like photon sorters. The 1300 nm-thick absorber achieves an average absorptivity of above 94% from 300 to 1000 nm and has great potential for photodetection and photovoltaic applications.