Electrically tunable and switchable perfect infrared absorber based on ENZ material

In this paper, a dynamically tunable and switchable perfect infrared absorber is put forward, which is composed of a gold ring array, an indium tin oxide (ITO) layer, an alumina (Al2O3) spacer and a continuous Au film from top to bottom. Epsilon-near-zero (ENZ) mode in ITO layer is excited by localized surface plasmon resonance (LSPR) mode of the gold ring. With the increase of the biasing voltage V, the carrier concentration of ITO material decreases, and the absorption peak caused by ENZ resonance blue shifts obviously. Notice that our infrared absorber can realize bidirectional switching of "ON" and "OFF" states at 1210 nm, with modulation depth of 70 % and switching contrast (SC) of 241 %, manifesting its excellent electrical regulation performance. After verification, the switching performance of our absorption structure has a high precision tolerate of the manufacturing process. A clear Fano type absorption curve appears in the wavelength range 1000 nm-1300 nm, under the biasing voltage V of 3.4 V. Moreover, a series of small absorption peaks are produced by Fabry-Pe ' rot (F-P) resonance in the horizontal plane caused by the standing wave in the ENZ layer, and this phenomenon is unexpected. We propose a theoretical interpretation for the absorption mechanism in both cases based on multiple interference model. It is also proved that the proposed infrared absorber is polarization insensitive and exhibits high absorptance (>90 %) over an incident range of 0 deg-60 deg. The electrically tunable absorption switch function makes our absorber have potential in selective thermal emitters, infrared sensors, infrared stealth, beam focusing and other fields.