High-Purity Multi-Mode Vortex Beam Generation With Full Complex-Amplitude-Controllable Metasurface

Vortex beam with inherent orbital angular momentum (OAM) is promising in high-capacity communication. On multimode vortex beam generation, metasurface has shown exceptional advantages of integration and miniaturization. For the current widely used phase-only methods on multimode vortex beam generation by metasurface, the purity of the OAM-mode spectrum is severely affected. A new method for generation of multimode vortex beam with high mode purity is proposed in this article by reconstructing the complete complex amplitude information on the meta-device aperture. A 20 dB suppression of the crosstalk modes is experimentally observed for the co-directional multimode vortex beam generation, which is much improved compared to the traditional phase-only scheme. In addition, the proposed scheme also provides the capability of generating high-purity multimode vortex beams with arbitrary preset propagation directions and power allocations. This study provides a platform for high-performance vortex beam communication by increasing the signal-to-noise ratio and enabling the multicasting scenarios with customized capacity requirements.