Polarization-insensitive Terahertz Graphene-based Optical Switches

We designed a single-layer patterned graphene metasurface composed of four L-shaped graphene strips, four rectangular graphene strips, and meter-shaped graphene block. Metasurface creates dual plasmon-induced transparency (PIT) through the interaction between light and dark modes. The transmission characteristics of the structure are analyzed using the coupled mode theory and the finite element method, and the structure realizes the function of the dual-frequency optical switch. At frequencies of 3.72 THz and 6.24 THz, the optical switch modulation amplitudes are 98.04% and 95.37%, respectively, and the corresponding insertion losses are 0.16 dB and 0.08 dB respectively. In addition, the proposed structure is insensitive to changes in the polarization angle of the incident light. Under the incidence of x-polarized light and y-polarized light, the PIT effect of the two structures is consistent. This research will present a new idea for the design of terahertz multi-frequency optical switches. The optical switch has great potential for various applications such as terahertz imaging, sensors, photodetectors, and modulators.