Numerical Analysis and Circuit Model of Tunable Dual-Band Terahertz Absorbers Composed of Concentric Graphene Disks and Rings
In this paper, periodic arrays of concentric graphene disks and rings placed near a metallic ground coated by a dielectric substrate are proposed and analyzed by a circuit model approach (CMA) to predict the absorption of the structure in the terahertz (THz) region. As numerical examples, single-band absorbers composed of graphene disks or graphene rings and a dual-band absorber composed of both graphene disks and rings are designed, presented, and proposed. In order to validate the accuracy of the results achieved by the CMA, numerical simulations based on the finite integral technique are applied. One of the significant features of the proposed structures is the tunability of the position of the absorption peak by controlling the chemical potential of the graphene patterns. An additional advantage of the proposed absorbers is that the absorption peaks of the dual-band absorber are stable for both transverse magnetic and transverse electric polarization with incident wave angles up to 70°. The proposed absorber could be used as an essential element in real-time THz detection and sensing systems.