Generation of optical vortices using the metasurface combining dynamic and geometric phases

Hitherto, methods to generate optical vortex beams have been widely researched, ranging from mode conversion to diffractive optical elements. However, bulky-sized traditional methods are unsuitable for nanophotonic systems, metasurface has become an alternative option for generating optical vortices. In this paper, a metasurface combining dynamic and geometric phases is proposed. Under the incidence of circular polarized light, optical vortices with different topological charges can be generated simultaneously by a single metasurface. The dynamic phase makes the topological charge of the vortex light vary with distance. The intensity distribution and relative distance of the focused vortices can be manipulated with different focal length of the metasurface. This method provides a new design to generate different vortices in a single device and has potential applications in particle capture and integrated optical systems.