A tunable graphene-based dual PIT device with dual-polarization excitation capability

Abstract

A simple dual plasmon induced transparency (PIT) device based on “Z” type and “circle-strip” combination is designed, which is composed of monolayer graphene. This structure has the capability to excite double PIT simultaneously in the x polarization and y polarization directions. The polarization direction of the incident light will change the resonance frequency of the horizontal and vertical bands, but the resonance frequency of the circular graphene in the middle is not affected by the polarization direction of the light. After comparing the transmission spectra of the single structure and the combined structure, combined with the analysis of the surface electric field, it is determined that the structure adopts the coupling method of bright-bright-bright mode to realize the double PIT function. In both x and y polarization directions, the three components of the device are capable of inducing dipole resonance. Additionally, simulation results fit well with the theoretical transmittance calculations. When the device is utilized as a light sensor, it has been observed that sensitivity tends to increase alongside Fermi level elevation. Specifically, under x polarization, sensitivity can reach 1.888THz/RIU with a maximum FOM of 9.28 when the refractive index of the analyte is 1.7. Meanwhile, under y polarization, sensitivity can reach 1.943THz/RIU with a maximum FOM of 7.61 when the refractive index of the analyte is 1.3. In its capacity as an optical switch, the device has demonstrated a maximum modulation depth of 80.6 % at 2.64THz under x polarization, and 73.29 % at 1.92THz under y polarization. All modulations are achieved by adjusting the Fermi level.