Generation of cylindrical vector vortex beams by two cascaded   metasurfaces
  We present a simple and efficient method to generate any cylindrical vector vortex (CVV) beams based on two cascaded metasurfaces. The metasurface works as a space-variant Panchratnam-Berry phase element and can produce any desirable vortex phase and vector polarization. The first metasurface is used to switch the sign of topological charges associated with vortex, and the second metasurface is applied to manipulate the local polarization. This method allows us to simultaneously manipulate polarization and phase of the CVV beams. 
Xunong Yi, Xiaohui Ling, Zhiyou Zhang, Ying Li, Xinxing Zhou, Yachao   Liu, Shizhen Chen, Hailu Luo, and Shuangchun Wen
physics.optics