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

•Actively switchable metasurface: The proposed metasurface design utilizes vanadium dioxide (VO2) films, allowing for active switching between different functionalities, such as broadband absorption and polarization modification.•Broadband absorption in metallic phase: The metasurface acts as a broadband absorber in the metallic phase of VO2, with an absorption rate exceeding 90% in the frequency range of 1.41–2.69 THz. This broadband absorption is achieved through an optimized metasurface structure.•Polarization conversion in insulating phase: When VO2 is in the insulating phase, the metasurface functions as a half-wave plate, converting the polarization of incident waves. It exhibits a polarization conversion rate (PCR) exceeding 80% in the frequency range of 0.71–2.72 THz.•Dynamic modulation of absorbance and PCR: The proposed metasurface allows for dynamic modulation of absorbance and PCR by varying the conductivity of VO2 within a specific range. This provides tunable performance for different applications.•Multifunctional wavefront manipulation: By introducing an abrupt phase at the interface, the metasurface enables arbitrary manipulation of reflected beams in the 1.0–2.2 THz broadband range. The design also includes 1D and 2D focusing metalenses with subwavelength focusing characteristics.•All in all, the scientific novelty lies in the integration of actively switchable metasurfaces based on VO2, offering broadband absorption, polarization conversion, and multifunctional wavefront manipulation capabilities in the terahertz frequency range. 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 pe