Reconfigurable multifunctional polarization converter based on asymmetric hybridized metasurfaces

Abstract

In the terahertz (THz) band, it is a challenge to integrate multiple functions into a very small unit cell structure of metasurface. However, the hybrid metasurfaces composed of several controllable materials provide a solution to this problem. In this paper, two multifunctional polarization converters based on asymmetric hybrid metasurface operating in the THz band are designed. The both polarization converters are designed with double-layer resonators that embedded by photosensitive silicon (Si) and vanadium dioxide (VO2) at the appropriate positions. By controlling the optical pump intensity and the temperature of the VO2, the designed metasurface polarization converter (MPC) I can realize the identical linear polarization conversion for both forward and backward reflection modes. When the external excitation conditions are changed, the polarization conversion frequency bands of forward and backward incident waves can be switched. Moreover, the MPC II can operate in both reflection and transmission modes and realize multifunctional polarization conversion. For the forward incident THz wave, the MPC II can perform two different functions under different excitation conditions: the conversion from co-polarization to cross-polarization in the reflection mode and the conversion from linear polarization to right-handed circular polarization (RHCP) or left-handed circular polarization (LHCP) in the transmission mode. While for the backward incident THz wave, the MPC II operates in the transmission mode and converts the electromagnetic (EM) wave from co-polarization to cross-polarization one. Our designs may provide a scheme for multifunctional integrated devices operating in THz band.