Synergistic dual plasmon-induced transparency effect based on incoherent coupling
Abstract
Plasmon-Induced Transparency (PIT) has emerged as a cutting-edge research focus in terahertz photonic devices due to its unique slow-light effect and exceptional optical field control capabilities. However, the current mechanisms for realizing dual PIT mainly rely on destructive interference between bright and dark modes. This work presents a single-layer metasurface composed of two longitudinal graphene strips, two transverse graphene strips, and a central graphene block. Based on the cooperative effect of incoherent coupling, we achieve a dual-PIT phenomenon in the terahertz frequency domain. Theoretical modeling based on Coupled Mode Theory (CMT) shows excellent agreement with Finite Difference Time Domain (FDTD) simulations. Further analysis reveals exceptional optical switching performance at a carrier mobility of <sc>3.0 m<sup>2</sup>/(V s),</sc> achieving a modulation depth of 97.31% with an insertion loss of <sc>0.10 dB.</sc> Moreover, the group index of the metasurface can reach 257. Most interestingly, by modulating the Fermi level of part of the graphene, we can switch between four-frequency channels and dual-PIT. This work not only enriches the evolution mechanisms of dual PIT but also advances the development of slow-light and optical switching.
