Planar Efficient Metasurface for Vortex Beam Generating and Converging in Microwave Region.

In this paper, single-layer transmission-type metasurfaces are proposed to generate a converged vortex beam and vortex beams with different topological charges. A new metasurface design is used to generate the vortex beam, in which the required accumulated phase difference along the propagation path is realized by designing and arranging artificial single-layer unit cells. Furthermore, the converged vortex beam is generated by metasurface that superimposes the phase distribution for the vortex beam and converged beam. The transmitted efficiency of the metalens can reach 20% as designed, which approaches to the efficiency limit of this type of metasurface. [ABSTRACT FROM AUTHOR]