Plasmonic Directional Couplers Based on Multi-Slit Waveguides

We propose and investigate the performance of the plasmonic directional couplers based on two dimensional multi-slit plasmonic waveguides, employing the finite difference time domain simulation method. The idea behind the directional properties of the directional couplers is the interference of two wave components, in and out of phase, at the coupled and isolated ports, respectively. The coupler is also analyzed by an analytic method. The simulation results comply well with those of the analytic considerations. The effects of variations of the coupler structural parameters, crosstalk between the input and output ports, and the overall structure loss are also investigated.