Tailoring orbital angular momentum of light in the visible domain with metallic metasurfaces

Submicron-thick gold films endowed with subwavelength patterning allow on-demand topological shaping of light, hence the precise delivery of optical orbital angular momentum. Several kinds of metallic metasurfaces enabling the generation of optical vortices with arbitrary topological charges in the visible domain are fabricated following a design based on space-variant subwavelength grating with discrete orientational distribution. The optical performances of obtained flat spin-orbit optical elements designed to operate at 532 nm wavelength are experimentally assessed and satisfactorily compared to expectations. About 80% of optical vortex generation purity for predetermined topological charge up to vertical bar l vertical bar = 10 is achieved. Other designs that allow continuous orientational distribution of nanogratings as well as the superposition of orbital angular momentum states are also proposed.