Multifunctional terahertz device with active switching between bimodal perfect absorption and plasmon-induced transparency

In this paper, we propose a terahertz (THz) micronano device that can actively switch between bimodal absorption and plasmon-induced transparency (PIT). The device mainly consists of a continuous top layer of graphene, an intermediate layer of silica and a bottom layer of vanadium dioxide, and has a simple structure, easy tuning and wide angle absorption. Through impedance matching and electromagnetic field distribution, we explain the generation of perfect absorption with double peaks. The simulation and multiple reflection interference theory (MRIT) show that the device achieves perfect absorption at 3.02 THz and 3.68 THz, and is highly sensitive to environmental refractive index, with a sensitivity of 1.1 THz/RIU. In addition, when the PIT effect is realized through the phase change characteristic of VO2, the device not only has the function of three-frequency asynchronous optical switch, but also has a strong slow light effect, and the maximum group delay (τg) is 35.4 ps. Thus, our design allows simultaneous switching, modulation, sensing, and slow light functions in the optical path and will greatly facilitate the development of THz multifunctional devices.