A compact broadband metamaterial absorber with miniaturized design based on graphene

Graphene-based metamaterial absorbers are increasingly popular for developing various reconfigurable and electrically tunable optical devices, especially in the terahertz (THz) range. This paper aims to design a broadband THz metamaterial absorber (MMA) based on graphene. The proposed absorber consists of a patterned graphene surface layer, a dielectric layer, and a bottom metallic film. The patterned graphene surface layer is composed of two parts with different slots to induce multiple plasmonic resonances. CST simulation results show that the bandwidth with an absorption efficiency exceeding 95% is 3.12 THz, ranging from 4.01 to 7.13 THz. We validated the simulation results using multi-reflection interference theory. To explore the physical mechanisms of broadband absorption, the distribution of the surface electric field in the structure was studied. We also found that the absorber exhibits polarization insensitivity and wide-angle incidence characteristics. The absorption frequency of the absorber can be tuned by changing the chemical potential of graphene. Some notable features of the proposed absorber include the maximum bandwidth and minimal unit cell size of a single-layer absorber without sacrificing polarization insensitivity or amplitude tunability. Besides, the absorber has a thickness of 7.2 μm and a unit cell period of 4 μm, thus its structure is very compact in comparison with most previous MMAs. This proposed MMA has potential applications in terahertz detection, filtering, imaging and stealth technology.