Controllable optical tweezer and spanner in evanescent fields via a single plasmonic metasurface

Abstract

A dual-functional plasmonic metasurface is proposed to realize trapping and rotation of microparticles in evanescent fields by simply changing the polarization of incident light. The metasurface is constituted with subwavelength rectangular nanoslit that is perforated in an Au film on the glass substrate. Simulated near-field intensity distributions show that surface plasmon vortex with designed topological charge and focused point with enhanced intensity can be controllably generated in the center region of the designed metasurface by different circularly polarized lights. Calculated optical force and optical potential on a polystyrene sphere further demonstrate the good performances of rotating and trapping a microparticle with the generated vortex and focused surface plasmon polaritons. Moreover, two examples designed with different topological charges demonstrate the flexibility of these metasurfaces in tuning the rotation radius of microparticles. The advantages of the proposed metasurface in design flexibility, multifunctionality, and small size may provide new possibilities for applications of integrated optical manipulation devices and systems.