Two new broadband and tunable terahertz pyramid patch/disk absorbers based on graphene metasurface

Abstract

In this work, an efficient circuit model of functional thin-film graphene-assisted metamaterial devices with exploiting transmission line theory is presented. The design is done by the usage of a MATLAB code analytically and the numerical results are obtained by the Finite Element Method (FEM) to verify the accuracy and validity of the circuit model approach. This paper proposes two new broadband graphene metasurface absorbers at terahertz frequencies. At first, a metasurface absorber consisting of pyramid graphene patches separated by dielectric layers is introduced. For most absorber applications, the bandwidth of the absorber is one of the most remarkable metrics. The obtained normalized absorption bandwidth for this absorber is 83.85 % for 90 % absorption with a bandwidth of 4.57 THz. To attain broad frequency bandwidth, we design the metasurface absorber consisting of disk graphene and extract its circuit model. There is good agreement between the results of the circuit model and those of the full-wave simulations. Also, the obtained normalized absorption bandwidth is 82.57 % for 90 % absorption with a bandwidth of 4.74 THz. The suggested method is easy and general, so we can apply it to the design and the simulation of other subwavelength structures in the wide frequency range from terahertz (THz) to visible regions.