Multifunctional terahertz device optimized based on particle swarm optimization algorithm

In order to expand the application scenarios of terahertz(THz) devices, we have designed a THz multifunctional device consisting of an electrically tunable graphene metamaterial in the top layer, silicon dioxide in the middle layer, and vanadium dioxide (VO₂), a phase change material, in the bottom layer. Particle Swarm Optimization (PSO) is used to optimize the structure of the multifunctional device. After several iterations, the ideal values of structural parameters were determined as h₁ = 6.35 μm, w = 3.93 μm, R = 5.00 μm and L = 21.97 μm. The device is a graphene-dielectric-metal structure when vanadium dioxide is in the metallic state, and the absorbing layer is a graphene layer at this time. The simulation results show that the devices achieves 99.94 % and 99.98 % complete absorption at 3.805 THz and 4.15 THz, with Q values of 37.04 and 36.09, respectively, and is highly sensitive to the environmental refractive index, with a sensing sensitivity as high as 1210 GHz/RIU. When vanadium dioxide is in the insulating state, the device realizes the plasmon-induced transparency effect and has excellent slow light performance, and the group delay is 30.71 ps. In a word, the design of this paper will provide more ideas for the research of new devices such as terahertz detectors, terahertz astronomical observation equipment and THz spectrometers.