Binary plasmonics: launching surface plasmon polaritons to a desired pattern.

We propose a binary plasmonic method to design the binary plasmonic structure (BPS), which is used to launch surface plasmon polaritons (SPPs) to a desired pattern. The BPS is composed of binary pixelated grooves. When a plane wave illuminates the BPS perpendicularly, the relative phases of the launched SPPs are determined by the positions of the grooves, which are designed by a simulated annealing algorithm. Here, we obtain single, three, and five SPP focal spots along the line parallel to the BPS, respectively, and three focal spots, which are located at the apexes of a triangle. The experiment agrees well with the numerical simulation.