Optical Metasurfaces for Generation and Superposition of Optical Ring Vortex Beams

The helical phase structure of a twisted light beam has attracted big interest in both fundamental science and practical applications. A facile metasurface approach to generate and manipulate ring vortex beams is reported and experimentally demonstrated. The generation of ring vortex beams is realized by combining the functionalities of an axicon, a vortex beam generator and a beam deflector onto a single reflective metasurface, which consists of nanorods with spatially variant orientations sitting on a silicon dioxide layer in the middle and a gold layer at the bottom. By controlling the polarization state of the incident light, the superposition of ring vortex beams is continuously tuned. The unique property of the developed device renders this technology very attractive for polarization detection and quantum science related applications.