Dual-band terahertz absorber based on graphene periodic arrays of disks and ribbons: circuit model approach

Abstract

A dual narrow band perfect THz absorber is presented in this work. The structure includes three layers of graphene ribbons, disks, and sheet on the TOPAS dielectric layer while a golden plate is placed at the bottom to act as a fully reflecting mirror against THz waves. According to the simulations, the device is robust enough to show independent operation versus layers thicknesses variations, chemical potentials mismatches, and changing of electron relaxation time. The designed THz absorber in this work is an appropriate basic block for several applications in THz optical systems such as sensors, detectors, and modulators. The layers in the proposed device are modeled via passive circuit elements and consequently, the equivalent circuit of the device is calculated. Leveraging developed circuit model and impedance matching concept, the proposed device is designed to perfect absorption at 1 THz and 7 THz. Ample simulations are performed using MATLAB and CST to verify the superior performance of the device. The presented manuscript considers the circuit model representation for three different layers of the device. For a unique structure, highly tunable response versus chemical potential is obtained. Circuit model approach and impedance matching theory are exploited to reduce computational time regarding conventional approaches.