A multi-functional vortex beam generator based on transparent anisotropic metasurface

Vortex beam generators are increasingly in demand for their enormous potential in improving communication capability. Along with the continuous integration of electronic product, devices with single function cannot satisfy the requirements of the people. Here, by employing an anisotropic metasurface (MS), we propose a transparent multi-functional vortex beam generator to obtain vortex beams with reconfigurable polarization status. An anisotropic element is firstly optimized to control x- and y-polarized wave independently, and then is applied to assemble a vortex beam generator that is not only able to convert spherical wavefront into a vortex one but also able to transform linearly polarized mode into the circular polarized counterpart. Interestingly, the polarized status of the generated vortex beam changes from x-polarization to left hand circularly polarization (LHCP) to y-polarization and finally to right hand circularly polarization (RHCP) when the spot source is rotated with different angles. For verification, the prototype of the practical configuration is fabricated and measured. Coinciding well with the simulated results, the measured ones show that linearly polarized spherical wave has been converted into LHCP or RHCP vortex beams with operating efficiency of 85.8% or 83.3% respectively.