Application of tunable graphene metasurfaces with plasmon-induced transparency in terahertz optical switches

This study presents a theoretical and numerical analysis of the plasmon-induced transparency (PIT) effect in ‘can-type’ and ‘circle-type’ composite structures. The proposed metasurface consists of an array of PIT devices that combine two semi-elliptical graphene elements with central vertical strip and circular graphene configurations. The spectral results obtained through coupled mode theory (CMT) fitting show good agreement with those calculated using COMSOL simulations. Numerical simulations of the metasurface reveal that the PIT transparency window can be tuned by increasing the Fermi level, achieving amplitude modulation degrees of 96.3%, 45.9%, and 89.4% at corresponding frequencies of 2.10 THz, 3.40 THz, and 5.15 THz, respectively. Furthermore, the influence of carrier mobility on transmission spectra is investigated in detail. At a carrier mobility of 3 m 2 /(V · s), high-performance optical switches with modulation depths of 99.2%, 76.6%, and 97.3% are achieved, accompanied by excellent extinction ratios (20.8 dB, 6.3 dB, and 15.7 dB). Compared with other similar optical switches, the proposed design demonstrates significant advantages. In conclusion, the graphene metasurface presented in this work provides enhanced theoretical support for developing dynamically tunable graphene-based optical switches. These graphene-metasurface configurations show potential applications in mid-infrared photonic devices, offering theoretical significance for advancing terahertz-range dynamic integrated photonic components.