Dual-wavelength switchable perfect infrared absorber based on multiple ENZ materials

Abstract

A dual-wavelength switchable perfect absorber, comprised of a continuous Au film, an alumina (Al 2 O 3 ) spacer, an indium tin oxide (ITO) layer, double-layer Dysprosiumdoped cadmium oxide (CdO:Dy) films, and a gold ring array from bottom to top, is numerically designed in this paper. The epsilon-near-zero (ENZ) properties are determined by the carrier concentration of these ENZ materials. As for ITO material, the carrier (electron) concentration can be electrically modified by applying a biasing voltage V . And different growth conditions afford significant variation of carrier concentration in CdO:Dy layers. Via changing the biasing voltage V , we can achieve broadband and multifrequency absorption in our infrared absorber. Especially, the proposed infrared absorber demonstrates excellent electrical regulation performance, enabling bidirectional switching of "ON" and "OFF" states at dual-wavelength. We also further reveal the absorption mechanism by establishing quasi-Fabry-Pérot cavity resonance model. In addition, it is shown that the infrared absorber can tolerate a wide range of incident angles as well as has polarization insensitive features by verification. This device has great potential in numerous optoelectronic applications, such as invisibility cloaking, sub-diffraction imaging, and thermal emission.