Perfect absorber with high sensitivity based on hexagonal star graphene surface

Abstract

Graphene absorbers have attracted wide attention due to their high absorption rate and narrow bandwidth in the terahertz field. In this study, we proposed a dual-band terahertz tunable perfect absorber designed with a hexagonal star ring and a circular ring monolayer graphene metasurface, which exhibits tunable, polarization-insensitive, and high sensitivity characteristics. The graphene absorber was simulated by using the finite element method and validated by using the impedance matching method. Simulation results show that this structure has two perfect absorption peaks at 4.8 and 8.04 THz. The variation of the dielectric layer material was analyzed, and the parameters of the structure and the intrinsic graphene parameters were adjusted to control the absorption efficiency of the dual-band absorption peaks. Simulation results show that the high symmetry of the structure brings incident and polarization-insensitive properties, maintaining absorption higher than 98% over a wide range of incident and azimuth angles. The sensing performance of the device was investigated by varying the ambient refractive index, and the highest sensitivity parameter S of the absorber reached to 2.375 THz/RIU. These results demonstrate that this high-sensitivity sensor has great potential for terahertz imaging and microstructure detection.