A terahertz tunable attenuator based on hybrid metal-graphene structure on spoof surface plasmon polaritons waveguide

A novel type of tunable attenuator on spoof surface plasmon polaritons (SSPP) waveguide based on hybrid metal-graphene structure for terahertz applications is proposed in this paper. Two structures are analyzed and designed, where the first is composed of a graphene sheet at only one cell of the SSPP waveguide and the second at all cells. By varying the graphene chemical potential via a biased voltage, the surface conductivity of graphene can be adjusted. Therefore, the attenuation can also be adjusted. Moreover, an equivalent circuit model is proposed to facilitate the designs of the proposed attenuator and offer the general understanding of the attenuation mechanism. Numerical simulation results with the CST simulator and WCIP method have a good agreement with the theoretical results. The simulated results show that the attenuator can obtain adjustment range from 6.02 to 14.32 dB for the first structure and from 1.58 to 30.93 dB for the second, as the chemical potential rises from 0 to 0.5 eV.