Slow-Light and Sensing Performance Analysis Based on Plasmon-Induced Transparency in Terahertz Graphene Metasurface

In this article, a polarization-independent graphene metasurface structure is designed to realize the excellent functions of slow-light and sensing generated based on plasmon-induced transparency (PIT) in terahertz (THz) region. The structure includes a cross-shaped and four square graphene resonators that are identical. The unique PIT transparent window generated by bright-bright mode coupling is studied by using finite difference time domain (FDTD) and coupled mode theory (CMT), which are highly consistent. By changing the Fermi level and carrier mobility of graphene, the transmission spectrum of PIT can be tuned effectively. Interestingly, due to the field enhancement and strong dispersion properties of surface plasma, the graphene metasurface proposed in this article has excellent effects in slow-light, and the maximum group index can reach 658. At the same time, because the transmission spectrum of PIT is sensitive to the external refractive index, the sensitivity and figure of merit (FOM) used to evaluate the sensing performance of the structure are 1.7134 THz/RIU and 144.45, respectively. Finally, because the graphene metasurface is a center symmetric structure, it has polarization-insensitive performance. The proposed structure can be used as a slow-light device or applied to biomolecular recognition, environmental monitoring, and other THz sensing fields.