Generation and controlled routing of single plasmons on a chip

We demonstrate the excitation of single surface plasmon polaritons on a silver nanowire using a nitrogen vacancy center and the subsequent controlled coupling to a second silver nanowire. The coupling efficiency and thus the splitting ratio between the nanowires is controlled by adjusting the gap size between the wires with an atomic force microscope. By numerical methods, we estimate the splitting ratios for different gap sizes, and the results support the values obtained in the experiment.