Ultra-wideband absorption-polarization conversion function switchable terahertz metamaterial

This paper presents a bifunctional reconfigurable terahertz metamaterial device that integrates ultra-wideband absorption and high-efficiency broadband polarization conversion functionalities based on the phase-change material vanadium dioxide (VO₂). By exploiting the reversible insulator-to-metal phase transition of VO₂ near 68 °C, the device achieves dynamic switching between two distinct electromagnetic response mechanisms. When VO₂ is in its insulating state, the device operates as a broadband linear cross-polarization converter. Upon transitioning to the metallic state, the device functions as an ultra-wideband perfect absorber. The physical mechanisms underlying the dual functionality are elucidated through surface current distribution analysis, electric field monitoring, impedance matching theory, and equivalent electromagnetic parameter extraction. Comprehensive parametric studies reveal the influence of key structural dimensions on device performance, while angular dependence analyses demonstrate excellent polarization insensitivity and wide-incidence-angle stability in both operational modes. Compared with recently reported terahertz devices, the proposed design exhibits superior bandwidth performance, compact structural dimensions, and dynamic functional reconfigurability, making it a promising candidate for applications in intelligent stealth systems, terahertz imaging, optical switching, and advanced communication technologies.