Refractive index sensing of spoof surface plasmon polaritons excited on graphene strips based on cylindrical dielectric metasurface coupling

In this paper, we present a novel terahertz plasmonic sensing concept that utilizes a metasurface coupler to excite spoof surface plasmon polaritons (SSPs) modes on graphene strips. The dielectric metasurface unit cell consists of two silicon cylindrical rods with different radii on a quartz substrate. Vertically incident terahertz waves are deflected by the metasurface, resulting in a transverse wave-vector within the substrate that matches the SSPs wave-vector supported by the graphene strips. This enables efficient excitation of SSPs modes on the graphene strips surface, leading to absorption resonances in the range of 0.420–0.430 THz with a high quality (Q) factor of 152. We then applied this device for refractive index sensing, and the investigation results indicate that the high Q resonances in the absorption spectrum experience shifts with changes in the refractive index of the target substance, with a sensitivity of 110 GHz/RIU. The designed structure in this study exhibits significant potential for applications in trace substance absorption spectrum detection.