Multi-band circuit model of tunable THz absorber based on graphene sheet and ribbons

Terahertz (THz) absorbers due to the high potential of providing reliable applications in modern devices and technology are increasingly being investigated. Recently, a dual-band THz absorber based on a graphene sheet and ribbons has been proposed in which the results were obtained using Full-wave simulations and its authors have not provided any specific design method. In this work, we have proposed and investigated that tunable THz absorber by its circuit model. A developed transmission line method beside the analytical circuit model of graphene continues sheet and periodic arrays of graphene ribbons are used to obtain analytical expressions for the circuit model. Here, first of all, we have compared the results of the proposed method with the results of that paper and secondly, using impedance matching concept we have proposed multi-band tunable THz absorber with near-unity absorption by the same structure. Then, we have compared the results of our circuit method with the Full-wave simulations. In either case, our proposed method in addition to excellent performance in terms of runtime and memory sources, has an acceptable agreement with the results of the Full-wave simulations. The proposed method is general and can be applied to design and simulate the other sub-wavelength structures.