Tunable terahertz graphene metamaterial optical switches and sensors based on plasma-induced transparency

A periodic metamaterial comprising three graphene-strips and four C-type graphene square-ring is proposed herein to realize plasmon-induced transparency (PIT). Based on the characteristics of graphene dynamic modulation, we effectively broaden of the transparent window the relative bandwidth to realize the broadband PIT. The influence of the polarized light angle on PIT is investigated, demonstrating that the polarization angle affects PIT significantly, the dynamic change from multiple plasma-induced transparency to single-PIT can be realized. By tuning the Fermi levels in the graphene, our proposed metamaterial structure allows preparing not only a multi-frequency optical switch with modulation degrees of the amplitude (MDA) up to 95.6% and insertion loss (IL) down to 0.315 dB at 5.35 THz but also preparing optical switches with MDA > 90% and IL < 0.35 dB in bands ranging from 5.28 to 5.48 THz. The refractive index sensitivity of metamaterials is also investigated, and the simulation results show that a sensitivity of 0.7 THz/RIU is achieved, meaning an excellent sensors can be prepared. Thus, the proposed structure provides a new idea for the design of terahertz multi-frequency switches and refractive index sensors.