Multifunctional vanadium dioxide-based terahertz metasurface with ultra-wideband, narrowband switching and polarization selection

In this study, a multifunctional terahertz (THz) metasurface based on vanadium dioxide (VO₂) is proposed and demonstrated. Under the external stimulus of thermal, the proposed metasurface can achieve ultra-wideband absorption, perfect narrowband absorption and polarization selection by leveraging the phase transition characteristics of VO₂. In its metal state, VO₂ enables the metasurface to function as a THz broadband absorber with an absorption efficiency exceeding 90% across a broad frequency range, exhibiting minimal polarization sensitivity. Conversely, in its insulating state, the metasurface operates as a narrowband absorber. The asymmetric split ring structure exhibits near-perfect absorption (>99.7%) for TE-polarized waves at 8.663 THz and complete reflection for TM-polarized waves, enabling effective polarization selectivity with a polarization extinction ratio of 25.15 dB. Through the analysis of impedance, electric field and surface current distribution, the absorbing mechanism is explained in detail. Additionally, we considered the impact of structural parameters and incident angles on the performance. The innovation and high performance of this metasurface provide a broader idea and method for the design of THz detectors, and have important application prospects in the fields of THz detection, modulation, and optical switches.