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

Realisation of a perfect absorber A=1 with transmittance and reflectance T=R=0 by a thin metasurface is one of the hot topics in recent nanophotonics prompted by energy harvesting and sensor applications (A+R+T=1 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 A>95% with simultaneously occurring anti-reflection property (R<5%) 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.