Dual functional Device Featuring Absorption and Polarization Conversion Based on Temperature Controlled Metasurface for Terahertz Applications

This study presents the development of a dual-functional terahertz device based on a metasurface layer combining metallic and vanadium dioxide (VO ₂ ) elements. The proposed metasurface is controllable through the temperature-tuning properties of VO ₂ and leads to the performance of absorption and polarization conversion with metal-insulator transition properties of VO ₂ . The unit cell of the proposed structure consists of a metasurface layer including a metallic large square ring with four gaps filled by VO ₂ , alongside a smaller VO ₂ square ring deposited on dielectric layer above a reflective ground plane separated by an air spacer. VO ₂ exhibits a reversible metal–insulator phase transition at 68°C, which is accompanied by a remarkable change in both electrical and optical properties. At room temperature (298 K), where the VO ₂ is in the insulating state, the metasurface operates as a linear-to-linear cross polarization converter (LTLPC) over a frequency range of 0.66 to 1.7 THz, achieving an 88% fractional bandwidth (FBW). When heated above 351 K, VO2 transitions to its metallic state, and the metasurface functions as an absorber with over 80% absorptivity across a frequency range of 0.34 to 1.96 THz, corresponding to a fractional bandwidth of 140%. The proposed structure offers significant advantages including simplified geometry, ease of fabrication, and enhanced performance, particularly in terms of bandwidth. This design not only dominates the deficiency of existing terahertz technologies but also suggests new possibilities for applications in the switchable and reconfigurable devices in terahertz measurement and communication systems.