Design, Theory, and Circuit Model of Wideband, Tunable and Polarization-Insensitive Terahertz Absorber Based on Graphene

Abstract

We present a wideband tunable absorber which is insensitive to polarization in terahertz region. This absorber is composed of dielectric and graphene sheet layers with crossover elliptical dielectric cylinders on top of the structure. Graphene plasmon resonances are used to achieve wideband absorption with relative bandwidth of 68% for the absorption above 90% in THz regime. Thanks to the symmetric design, the structure is polarization-insensitive. Furthermore, the absorber has a good performance for wide angle of the incident waves. Also, the equivalent circuit model of the absorber is derived and the results are in good agreement with the simulation ones. The presented method for broadening the absorption spectrum and the technique of equivalent circuit model derivation can be used for related structures which have many applications in similar devices.