Vanadium dioxide thin films-assisted terahertz meta-surface for simultaneous absorption, polarization conversion bi-functional switching, and wavefront operation

Actively switchable metasurfaces are extremely useful for achieving a multifunctional integrated platform. The proposed design enables functional switching through the temperature-induced phase transition features of vanadium dioxide (VO2). The hypothesized metasurface can be considered a broadband absorber when VO2 is in the metallic phase, with an absorption rate approaching 90% in the frequency spectrum of 1.41–2.69 THz, according to numerical simulations. When VO2 is in the insulating phase, the proposed metasurface acts as a half-wave plate with more than 80% polarization conversion rate (PCR) in the frequency range of 0.71–2.72 THz. Furthermore, the dynamic modulation of absorbance and PCR can be achieved when the VO2 conductivity varies within a specific range. Finally, by changing the opening angle of the gold split-ring resonator to introduce an abrupt phase at the interface, the composed metacell can perform arbitrary manipulation of reflected beams in the 1.0–2.2 THz broadband range; we also design 1D and 2D focusing metalenses. Both have good subwavelength focusing characteristics. Therefore, the proposed metasurface can be effectively applied in sixth-generation communication systems, terahertz imaging, and other technologies.