Design of Perfect Absorber Based on Metagratings: Theory and Experiment

This article proposes an analytical design methodology for different kinds of perfect absorbers (PAs) based on metagratings (MGs). In the specific analysis and design, the period of the MG is chosen to ensure that there is only the $0^{\textrm {th}}$ order diffraction mode. Using the established theory, the supercell of the MG is rigorously analyzed to derive a specific load impedance density expression that allows achieving destructive interference of specular reflection of the substrate and $0^{\textrm {th}}$ mode diffraction such that perfect wave absorption is realized. Four kinds of PAs composed of different supercells of MG with different bandwidths are systematically analyzed, designed, simulated, and experimentally verified. The simulation and measurement results are in good agreement and consistent with the theoretical analysis, showing the validity of the provided theory and technique for electromagnetic wave absorption.