Optical Metasurfaces for Grafted Vortex Beams Generation

Inspired by plant grafting, the act of placing a portion of one plant (scion) on a branch or root of another (rootstock), grafted vortex beams (GVBs) can be formed through grafting two or more helical phase profiles of optical vortex beams. GVBs have attracted much attention due to their unique optical properties and potential applications. Here, we propose and demonstrate the coaxial superposition of GVBs without relying on the complicated optical setup. The coaxial superposition of GVBs can generate asymmetric singularity distribution, which can be modulated by introducing an initial phase difference in the metasurface design. Our work has provided a compact metasurface approach to complete the sophisticated task that is extremely challenging or impossible with conventional optics, opening opportunities for the study and applications of GVBs in a wide range of areas.