Bifunctional switchable terahertz metamaterial in the same operating band based on VO2

A bifunctional device is designed to provide flexible control of broadband absorption and polarization conversion based on the insulator-to-metal phase transition material vanadium dioxide (VO2). When VO2 is metallic, the switchable metamaterial serves as a broadband absorber consisting of a VO2 square, the dielectric spacer, and VO2 film. According to the simulated results, the designed system can obtain more than 90% absorption from 2.62 THz to 6.65 THz with a relative bandwidth of 86.95%. The broadband absorption is unaffected by polarization attributed to the symmetry structure, and it still performs effectively up to incidence angle of 60°. When VO2 is insulating, a simple anisotropic metamaterial is used to construct a terahertz polarization converter. The numerical calculation shows a linear polarization conversion rate over 90% from 2.2 THz to 6.9 THz, with a corresponding relative bandwidth of 103.2%. The above structure features high efficiency, wide-angle and broad bandwidth advantages. In addition, the design exhibits dual function that can yield broadband absorption and polarization conversion in the same operating band, which opens up new avenues for the development of switchable devices for potential applications in stealth and communications.