Plasmonic metasurfaces for far-and near-field orbital angular momentum manipulation

Abstract

Optical beam carrying orbital angular momentum(OAM) exhibits profound potential in optical communications, micromanipulation and other related fields due to its helical wavefront. However, complex configuration of manipulating optical vortices have hindered the realization of nanophotonic systems. Recently, owing to the ultrathin structure, plasmonic metasurfaces based on abrupt phase shift have aroused appreciable interest. In this paper, we introduce a multifunctional device that integrates a focusing apparatus and an orbital angular momentum generator by the use of the plasmonic metasurfaces. This metasurface combining Archimedean spirals and spatially variant nanoslits achieves plasmonic focusing and an optical needle in the near- and far-field, respectively. Moreover, generation of optical vortex beams is shown in the far- and near-field simultaneously, where light field can be arbitrarily manipulated. We expect this work to have further applications in integrated photonic systems.