Polarization and angle insensitive ultra-broadband mid-infrared perfect absorber

Abstract A new polarization and angle insensitive ultra-broadband perfect absorber (UPA) was proposed and demonstrated based on an alumina-chromium-alumina-chromium four-layer structure. The absorption bandwidth reached 3059 nm in the infrared range (from 939 nm to 3998 nm) with a spectral absorptivity greater than 90%. The average absorption was up to 94.0% in a range of 800 nm to 4200 nm. The physical mechanisms and influence of different structural configurations on the absorption performance of the UPA were analyzed in detail. When the oblique incidence angle was up to 60°, the average absorption rates of the TE and TM modes were 87.3% and 85.0%, respectively. The proposed UPA has potential applications in thermo-photovoltaics and infrared detection.