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

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 degrees and a flat-top 75% absorption over a wideband of 1.74 microns for an angle of incidence of 50 degrees in the middle wave infrared region. (c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement