Integrating two epsilon-near-zero materials into planar multilayer metamaterial structure for broadband near-perfect mid-IR absorption

Abstract

Absorptive metamaterials composed of antimony-doped-germanium of different epsilon-near-zero wavelengths and germanium films are designed and fabricated for broadband perfect light absorption around the epsilon-near-zero wavelengths. By integrating two bilayers separated by a semiconductor spacer into a metamaterial structure backed by substrate and gold thick ground plane, we realize more than 93% P-polarized light absorption over a wavelength range of 1.8 microns for an angle of incidence of 40° and a flat-top 75% absorption over a wideband of 1.74 microns for an angle of incidence of 50° in the middle wave infrared region.