We propose a three layered metal-graphene-metal metasurface to investigate the controllable linear asymmetric transmission and perfect polarization conversion in THz regime, by using the finite-difference time-domain (FDTD) method. An on-to-off control of asymmetric transmission and perfect polarization conversion is achieved by changing the Fermi energy of graphene from 0.8 eV to 0 eV. We present the electric field distribution and Fabry-Perot-like cavity model to analyze the working mechanisms. By gradually shifting the Fermi energy of graphene, two functions are realized, i.e., controllable linear asymmetric transmission and controllable total transmission with near perfect polarization conversion.

We propose a switchable THz metamaterial that can be switched between two functions of half-wave plate and quarter-wave plate. The two switchable functions can be simply achieved by inserting a VO₂ film in the metamaterial design. Finite-difference time-domain (FDTD) simulation results show that the proposed metamaterial can convert x-polarized incident wave to y-polarized reflected wave when VO₂ is at metal phase, and convert x-polarized wave to circularly polarized wave when VO₂ is at insulator phase. The metamaterial performs well in the two functions, i.e., the same broad working frequency band and near perfect polarization conversion. The switching effect originates from the switchable Fabry–Pérot cavity length induced by the phase change of VO₂. We believe that our findings provide a reference in designing switchable metamaterials.

We propose a graphene based metasurface to investigate the function of switchable polarization selective wave manipulation in THz regime by using the finite-difference time-domain (FDTD) method. The proposed metasurface consists of two layers of graphene arrays, polymer dielectric spacer and a gold mirror film, which can be switched between two states by simply biasing the two graphene layers ON and OFF with the designed voltage and zero voltage without reconfiguring the Fermi energy distribution. One state is for x polarized wave manipulation and the other is for y polarization incidence. Then, the functions of switchable polarization selective anomalous reflection and focusing effect for 6 THz wave are realized by configuring the structure with specific values of Fermi energy. Moreover, we also designed the structure to focus at other spatial positions and another working frequency of 5.5 THz by reconfiguring the Fermi energy distributions.

We proposed a vanadium dioxide (VO₂)-integrated multi-functional metamaterial structure that consists of three metallic grating layers and two VO₂ films separated by SiO₂ dielectric spacers. The proposed structure can be flexibly switched among three states by adjusting temperature, incident direction, and polarization. In state 1, the incident wave is strongly transmitted and perfectly converted to its orthogonal polarization state. In state 2, the incident wave is perfectly absorbed. In state 3, incident wave is totally reflected back. The working frequency of the multi-functional metamaterial can be arbitrarily tuned within a broad pass band. We believe that our findings are beneficial in designing temperature-controlled metadevices.

We propose a graphene and strontium titanate (STO) integrated terahertz metasurface that can achieve the flexible manipulation of plasmon-induced transparency (PIT) effect. The proposed structure consists of a doped Si substrate, a SiO₂ spacer, and a STO film with graphene antennas and Indium-Tin-Oxide (ITO) nanowhiskers electrodes patterned on it. By separately biasing the graphene antennas, the bright-bright mode coupled PIT effect is achieved. By flexibly configuring the Fermi energy distributions on the graphene antennas, the shape of PIT spectrum is also flexibly manipulated. Moreover, the working frequency band can be shifted by changing the environmental temperature due to the temperature dependent permittivity of the STO film. Our findings are beneficial in designing flexibly manipulated THz devices.