High-performance multi-frequency optical switch based on tunable quadruple plasmon-induced transparency in monolayer patterned graphene metamaterial

A monolayer graphene metamaterial structure with a periodic pattern of transverse graphene strip and semi-enclosed graphene square ring is proposed. The dynamically tunable quadruple plasmon-induced transparency (PIT) effect is achieved in the terahertz band. The strong destructive interference between the bright mode and the dark mode, the electric field distributions of the composite graphene structures explain this quadruple-PIT phenomenon well. The results obtained by finite-difference time-domain (FDTD) simulation agree well with those calculated by the coupled mode theory (CMT). By modulating the Fermi level of graphene, two hexa-frequency asynchronous switches and two quadruple-frequency synchronous switches are realized, their maximum modulation depth is 99.9%, and its corresponding insertion loss and extinction ratio are 0.10 dB and 29.90 dB, respectively. These excellent performances exceed many similar graphene metamaterial structures. Therefore, our proposed quadruple-PIT graphene metamaterial structure has potential application value for the design of terahertz multi-channel switches.