Polarization-sensitive tunable multi-band terahertz absorber based on single-layered graphene rings

In this paper, a metamaterial absorber is proposed, which is constructed by graphene rings and a gold film separated by an ultrathin SiO2 layer. The feature of this absorber is that the absorption bands can be adjusted either by applying external electric fields or by rotating the polarization angles of the incident electromagnetic waves. The calculation results show that the continuous tunable or two- to multi-band absorptions can be realized by the above two methods. Through equivalent medium theory and impedance-matching condition, the anisotropic absorption mechanism of this absorber is explained. Moreover, the simple specific design makes the absorption bands able to be further tuned by adjusting various parameters, such as the geometry sizes and relaxation times of graphene rings. Our results indicate that the absorber has great adjustability and great potential application in filtering, terahertz signal detection, signal parameter estimation, smart sensing, tunable absorbers, and cloaking.