Efficient Metacoupler for Complex Surface Plasmon Launching

Surface plasmons (SPs) promise versatile potential applications in many aspects and thus have been a subject of enormous interest. As the most essential functionality, efficient coupling of free-space light into complex SP field is of particular interest in current research. Most existing methods only focus on either efficient coupling or complex SP field generation, which is insufficient to support the ever-increasing demand of practical applications. Herein, it is demonstrated both theoretically and experimentally that a metasurface composed of properly designed C-shaped slit resonators can function as an efficient SP coupler. More importantly, it is shown that the phase and amplitude of the coupled SPs can be simultaneously manipulated, which would offer considerable design flexibilities for complex SP launching. This methodology can provide a wide platform for the design and fabrication of high-performance plasmonic devices in the future, especially large-area ones in practical applications.