Ultra-thin midwavelength infrared absorber using bismuth based planar thin film metamaterials

We reveal the extraordinary potential of bismuth (Bi) based planar thin film metamaterials in achieving light perfect absorption for midwavelength infrared (MWIR) range from 3 to 6 μm. The proposed absorber is composed of an ultra-thin Bi film and a continuous metallic film separated by a dielectric spacer. Theoretical analyses show that the absorber exhibits narrowband absorption that can continuously span the whole MWIR range by varying the geometric parameters. Furthermore, it is found that the absorber displays wide-angle absorption up to 80° as well as polarization-insensitive properties. Experimental measurements are performed to corroborate the theoretical analyses.