A polarization insensitive terahertz tri-band graphene metasurface absorber

A graphene-based tri-band perfect metasurface absorber is presented for the far-infrared frequency range. A two-dimensional periodic pattern of graphene patches is created on a thin SiO2 dielectric layer, which is backed by a gold ground plane of sufficient thickness ( t ) ensuring zero transmission of the impinging electromagnetic (EM) wave. An array of graphene elliptical discs is placed around graphene square patches and thin graphene strips are used to connect these elliptical patches to the square patches. In terms of the lowest frequency of absorption, the proposed absorber seems to be a thin one as t similar to lambda max/13. It is also considered compact because the periodicity of the cells is on the order of lambda max/22. The absorption spectrum gives three perfect absorption peaks with absorptivity greater than 99% at 5.76 and 9.06 THz. Further, the absorptivity is better than 96% at 7.86 THz. The performance of the proposed absorber remains invariant with change in polarization of the incident wave. It is revealed that this absorber performs satisfactorily throughout a broad angular range of incidence of about +/- 60 degrees.