Switchable terahertz broadband absorption and linear-to-circular polarization conversion

We proposed a switchable bifunctional metasurface for broadband absorber and linear-to-circular polarization converter (LTCPC) in terahertz regime. When vanadium dioxide (VO2) is in the metallic state, the designed metasurface acts as a broadband terahertz absorber. The results demonstrate that the absorptance is above 90% and the bandwidth ratio is 68.6% from 0.981 to 2.011 THz. When VO2 is in the insulated state, the proposed structure behaves as an LTCPC with ellipticities 1 and −1 in frequency bands of 0.391∼0.517 and 0.673∼2.363 THz, respectively. The axis ratio is lower than 3 dB. The designed metasurface provides a new method for designing multifunctional terahertz devices.