Terahertz four-channel polarization-multiplexed vortex beams based on vanadium dioxide integrated metasurfaces

In recent years, vanadium dioxide (VO2) has drawn enormous attention in dynamic electromagnetic (EM) manipulation, owing to its mild phase change condition and prominent diversity of optical characteristics. In this paper, anisotropic meta-atoms integrating VO2 are proposed to obtain four polarization-multiplexing channels. The meta-atom is composed of two stacking metal–insulator-metal (MIM) structures. For the modulation of EM wavefront in desired manners, a meta-atom database composed of 256 meta-atoms is elaborately designed. Applying the meta-atom database and the degree of freedom in interfacial phase distribution, two metasurfaces are demonstrated in the verification of four-channel polarization-multiplexed vortex beams. The firstly proposed metasurface realizes the generation of four vortex beams with different topological charges. Each channel is dependent on the polarization of the incident wave and VO2 state. The further investigated metasurface achieves simultaneous control over the reflection direction, quantity, and mode of vortex beams under different VO2 states and polarization states of incident wave. In addition, designed metasurfaces exhibit wideband effect for over 100 GHz. The proposed design method enables four-channel generation of vortex beams using a single metasurface, and may have potential applications in dynamic and integrated terahertz communication.