Detailed Experiment-Theory Comparison of Mid-Infrared Metasurface Perfect Absorbers

Realisation of a perfect absorber [Formula: see text] with transmittance and reflectance [Formula: see text] by a thin metasurface is one of the hot topics in recent nanophotonics prompted by energy harvesting and sensor applications ([Formula: see text] is the energy conservation). Here we tested the optical properties of over 400 structures of metal–insulator–metal (MIM) metasurfaces for a range of variation in thickness of insulator, diameter of a disc and intra-disc distance both experimentally and numerically. Conditions of a near perfect absorption [Formula: see text] with simultaneously occurring anti-reflection property ([Formula: see text]) was experimentally determined. Differences between the bulk vs. nano-thin film properties at mid-IR of the used materials can be of interest for plasmonic multi-metal alloys and high entropy metals.