Launching phase-controlled surface plasmons on Babinet metasurfaces.

Surface plasmons are electromagnetic modes bounded at the metal-dielectric interfaces, which have numerous applications due to the strong field enhancement effect. Therefore, controlling surface plasmons is in high demand for modern photonics and plasmonics. In this Letter, we propose a kind of metasurface for launching surface plasmons with a controlled phase based on the Babinet principle. The phase control is achieved by arranging C-shaped apertures on a metal surface that exhibits highly efficient electric dipole resonance. By properly designing the spatial separation and orientation of the aperture resonators, an arbitrary phase profile is achieved that allows anomalous (directional and focusing/diverging) surface plasmon launching and manipulation of the wavefront.