Directional Nanoslit-Bump Coupler for Surface Plasmon Polaritons

We investigate a p-polarized plane wave transmitted through a metallic slit--bump nanostructure using the finite difference time domain simulation. It is found that narrow bumps with suitable separation can diffract surface plasmons into highly directional collimating beams. The number and directionality of the beams can be controlled by adjusting the geometry parameters of the nanostructure. The structure with optimized parameters may be interesting for practical applications as directional nanoslit SPP-light coupler in integrated photonic devices.