Ultra-broadband tunable terahertz absorber based on graphene metasurface with multi-square rings

In recent years, thinness, lightness, broadband, high absorption, and tunability have become five important elements for electromagnetic (EM) absorbers. This article proposes a novel single-layered graphene metasurface absorber (GMSA) that perfectly achieves all of the above elements. The GMSA differs from common hybrid patterns in that it adopts a graphene layer with a simple multi-square ring structure. The simulation results show that Fabry-Perot resonance (FPR) and graphene-based surface plasmon resonance (GSPR) can be combined to produce the broadband absorption of 3.04 THz in the terahertz (THz) frequency range. The proposed GMSA is completely polarization-insensitive because of its symmetrical configuration, and it exhibits wide-angle oblique incidence properties for both TE and TM-polarized waves, allowing it to achieve broadband absorption with at least 90% absorption in the range of incident angles from 0° to 45°. In addition, the chemical potential of graphene can be altered to change the effective absorption bandwidth, which can be easily tuned by the applied external voltage. The GMSA has broad application prospects in THz detection, imaging, and object cloaking due to its flexible and straightforward construction, polarization insensitive, wide-angle incident, broadband, and high absorption qualities.