Highly stable dynamically controlled linear polarization converter for THz applications

This study presents a reflective linear-to-linear (L2L) cross-polarization converter (CPC) for terahertz (THz) applications. The unit cell features a modified wheel-shaped geometry, achieved by merging concentric circular rings of varying radii, placed on a polyimide substrate optimized for THz operation. The proposed design exhibits an ultra-wide bandwidth of 0.370 THz (0.345–0.715 THz) and achieves a polarization conversion ratio (PCR) exceeding 75% for most of the operational band. The polarization conversion mechanism is dynamically controlled via vanadium dioxide (VO2), a thermally responsive phase-change material. Below its threshold temperature (68°), VO2 remains in its insulating state, enabling efficient polarization conversion, while transitioning to a metallic state above this temperature suppresses the conversion entirely. Furthermore, angular stability analysis confirms robust performance under oblique incidence angles up to 50°, demonstrating its practicality for real-world applications.