Tunable ultra-wideband terahertz absorber based on graphene disks and ribbons

Terahertz frequency band has become one of the most interesting fields of research these days and the necessity of various modern applications in this area is THz absorbers. In this paper, we have proposed and investigated a novel ultra-wideband terahertz absorber by using periodic arrays of graphene disks and ribbons. Analytical circuit model of graphene arrays besides a developed transmission line theory is used to obtain analytical expressions for the input impedance of the proposed structure. The input impedance is adjusted to be closely matched to the free space impedance in a wide frequency range. Using three layers of patterned graphene, bandwidth of 90% absorption reached to 131% of central frequency. Regarding excellent performance of the proposed method in terms of computation time (showing more than 5 orders of magnitude reduction in runtime) and memory sources, this method with producing results with an acceptable agreement (with an error less than 5%) compared to the results of full-wave numerical modeling can be utilized in design of other graphene-based sub-wavelength devices.