Analytical design of tunable multi-band terahertz absorber composed of graphene disks

In this paper, the periodic arrays of multi-layer graphene disks placed near a metallic ground coated by dielectric spacers are proposed and analyzed by the Circuit Model (CM) based on the reflected fields to predict the perfect absorption response in the terahertz (THz) region. As numerical examples, single-, dual-, and triple-band absorbers with perfect absorption at three different THz frequencies are designed and proposed. The design is done by usage of a simple MAMAS code analytically and the numerical results are obtained by the Finite Element Method (FEM) to verify the accuracy and validity of the CM approach. The metallic ground restricted the transmission of the incident wave and all incident electromagnetic wave is confined between graphene disks and the metallic ground. As a result, a narrowband perfect absorption peak with full width at half maximum (FWHM) of (similar to)0.1 THz is obtained. The position of the absorption peak and also the number of peaks could be altered by control of the chemical potential of graphenes, indicating the tunability of the proposed structure. This structure supports the fabrication of THz devices such as optical filters, sensors, and active THz metamaterial devices.