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 degrees 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.