Chip-integrated polarization multiplexed metasurface for simultaneous generation of versatile terahertz vortices

Abstract

Terahertz vortex beams, carrying orbital angular momentum (OAM), are quite desirable for enhancing data transmission capability in telecommunication. However, it faces fundamental and technical challenges in a single metasurface to simultaneously generate orthogonal basis vortices with linear polarization (x- and y-polarity) and circular polarization (left- and right-handed polarity) under the orthogonal polarized light incident. Here, we proposed a chip-integrated all-dielectric metasurface in the terahertz regime, to demonstrate the simultaneous generation of four-channel orthogonal polarized vortex beams at various topological charges under the x- and y-polarized light incident. The polarization multiplexed metasurface was designed only with a propagation phase strategy, consisting of polarization-maintaining and polarization-conversion meta-atoms. Simultaneous control of polarization and topological charges in vortex beams was realized by properly arranging birefringent meta-atom arrays to induce additional phases of x- and y-polarization as customized, showing more degrees of freedom for carrying information. The experimental results are in good agreement with the simulations. Such a metasurface approach provides complete polarization bases for further synthesis of diverse polarization vortices required for huge-capacity communication.