Controllable transmissive-reflective multifunction terahertz metasurface by different polarization and operating frequencies

Due to the limitations of frequency bands and control methods, it is difficult to achieve multi-functional integration and real-time regulation of full-space metasurfaces. In this paper, we proposed a switchable transmissive-reflective mode terahertz metasurface independently depending on the incident wave frequencies and polarizations. The unit cell consists of four metallic layers, which are separated by three silicon dioxide layers. When the x-polarized wave is incident along the +/- z-axis, the meta-device achieves focusing function at 1.62 THz. When the y-polarized wave is incident along the +/- z-axis, the structure generates the reflective two and four splitting beams at a frequency of 0.82 THz and realizes a focused beam with a topological charge of l=+/- 1 at a frequency of 1.65 THz. The full wave simulation results are in good agreement with the theoretical calculation predictions. The metasurface provides a new idea for the control of terahertz devices, and has a broad application prospect in the field of terahertz systems.