Single-layer terahertz metasurface for multichannel vortex device based on polarization multiplexing

Orbital angular momentum (OAM) beams are special beams with helical phase distribution. The conventional methods for generating OAM beams primarily rely on devices such as spiral phase plates, cascaded lens, and spatial light modulators. However, these methods incur high costs and face challenges in meeting the demands for optical system miniaturization and integration. The appearance of metasurface provides a new platform for the generation of integrated OAM beams. In order to achieve low crosstalk multi-channel OAM multiplexing on a single-layer metasurface, this work researches the phase and amplitude characteristics of co-polarization and cross-polarization in the transmission phase generation process. In addition, under the normal irradiation of circularly polarized light, three OAM beams carrying different topological charges are successfully generated by adjusting the structural parameters and rotation angles of the unit. The proposed terahertz metasurface demonstrates the ability to control complex wavefronts and offers a new avenue for developing multi-channel terahertz metasurfaces.