Quadruple Plasmon-Induced Transparency Effect in Graphene Micro-Nano Structure and Its Applications for Switching, Sensing, and Slow Light

Abstract A single-layer graphene structure is put forward to generate quadruple plasmon-induced transparency (PIT) at the terahertz frequency by coupling the bright-dark mode and bright-bright mode originated from five graphene strips. Based on the research on the electric field intensity of the PIT transparent window, it is suggested that intense fatal interference occurs among the bright and dark modes. The PIT reaction of the structure is analyzed and simulated with the coupled mode theory (CMT) and the finite difference time domain (FDTD) approach. Tunable multi-frequency switching is achieved under this quadruple transparency effect, since the maximum modulation depth (MD) is as high as 95% and the minimum insertion loss (IL) is 0.17 dB. Besides, the time delay and the group refractive index within the PIT windows can be up to 0.744 ps and 722, respectively. The proposed structure shows another fascinating ability to be sensitive to the nearby refractive index with the sensitivity of up to 0.91 THz/RIU. Therefore, this structure offers another novel thinking to design the multichannel switches, slow light instruments, and sensors in the terahertz band.