Tunable terahertz double plasmon induced-transparency based on monolayer patterned graphene structure

In this paper, tunable double plasmon-induced transparency (PIT) is achieved in a monolayer-patterned gra-phene structure. The proposed structure is composed of a middle graphene-strip and two pi-shape graphene microstructures. Results show that the double PIT effect is originated from the destructive interference between two bright modes and one dark mode, a equivalent coupled mode theory (CMT) model is utilized to confirm the finite-difference-time-domain (FDTD) simulation. The influences of the chemical potential, scattering rate, and geometrical size on the double PIT transmission spectrum are investigated. The modulation properties of the proposed structure have been studied in detail and it shows excellent modulation depth (MD) and relatively low insertion loss (IL). Moreover, the proposed structure shows a maximum refractive index sensitivity about2.38 THz/RIU, and the maximum figure of merit (FOM) can reach 43.4. The effect of the refractive index of the substrate on the sensing performance is also investigated. Thus, the proposed structure can be applied in the areas of multi-function optical switches, terahertz slow light devices, modulators, and sensors.