Equivalent Circuit Model for the Design of Frequency-Selective, Terahertz-Ban Graphene-Based Metamaterial Absorbers

Microwave absorbers have a wide range of potential applications at L, S, C, X, and Ku bands. But the development of a broadband absorber at terahertz frequencies has been a challenge. Here, an equivalent-circuit model is used to design and analyze a graphene-based frequency-selective surface (FSS) terahertz metamaterial absorber in the range of 0.1 to 4.0 THz. The effects of the chemical potential of the graphene layer, dielectric layer thickness, and FSS unit cell dimensions (i.e., periodicity, strip width, gap, etc.) on the absorption capability were determined for the proposed structure. An optimum absorber with negative permeability has a peak reflection coefficient of -37.9 dB at 1.2 THz, with a graphene chemical potential of 0.35 eV. A -10 dB absorption bandwidth of 0.68 THz (0.79 to 1.47 THz) is predicted. The metasurface behavior of the device is demonstrated in terms of frequency-dependent impedance, effective permittivity, and permeability. The results demonstrate the effectiveness of the structure for practical applications in the terahertz regime.