Slow-light effects of plasmon-induced transparency based on patterned graphene metasurfaces

Enhancing light–matter interactions is particularly important in the field of micronano optics, which can be achieved through plasmon-induced transparency. A new type of metasurface consisting of a single layer of graphene is mainly investigated in the study. This structure is mainly composed of a graphene strip and two graphene blocks, generating plasmon-induced transparency at terahertz frequencies via weak coupling between the two bright modes. Furthermore, the time-domain finite-difference method (FDTD) and coupled-mode theory (CMT) are utilized to further explore the physical mechanism of PIT formation. By adjusting the Fermi level of graphene, the transmittance window of PIT can be effectively regulated, resulting in a reflectivity of more than 65% for this structure. Moreover, the influence of the graphene Fermi level on the slow-light effect was analyzed, and the group index was increased from 450 to 562 when the Fermi level of graphene was increased from 0.8 eV to 1.1 eV. The findings are important for the realization of multifunctional terahertz devices such as modulators and slow light.