Bi-functional metasurface for broadband absorption and broadband cross-polarization conversion based on vanadium dioxide

A bi-functional metasurface with switchable absorption and cross-polarization conversion in the terahertz band is proposed by using phase change material vanadium dioxide (VO2). When VO2 exhibits metallic property, the proposed metasurface acts as a broadband absorber. Simulation results show that the absorption rate of the absorber is greater than 90 % in the range of 1.485–3.575 THz, and the relative bandwidth is 82.6 %. The absorption efficiency can maintain above 90 % when the incident angle is less than 60° for TM wave. Due to the symmetry of the designed structure, the absorber is insensitive to the polarization angle. When VO2 exhibits insulating property, the proposed metasurface behaves as a broadband cross-polarization converter. Simulation results show that the polarization conversion ratio of the polarization converter exceeds 0.9 in the range of 1.1–3.2 THz, and the relative bandwidth is 97.7 %. Nearly 100 % cross-polarization conversion can be achieved at 1.51 THz, 2.356 THz and 3.1 THz. The proposed metasurface features high efficiency, wide-angle and broad bandwidth advantages, which has potential application value in imaging, stealth technology, radar detection and other fields.