Planar plasmonic focusing and optical transport using CdS nanoribbon.

Planar plasmonic focusing of surface plasmon polaritons (SPPs) by an in-plane nanostructure consisting of Ag-column arrays and an in-plane Fresnel zone plate (FZP) with a Cu grating underneath for energy compensation was demonstrated. The CdS-based hybrid plasmonic waveguide generated in the Ag-column arrays was characterized with a scanning near-field optical microscope. By using the FZP focusing structure, the SPP modes were separated from the CdS photoluminescence background and focused at the FZP focus area, and in this way, were used as the source for the SPP waveguide. Finite-difference time-domain simulations correspond with the experimental observations, suggesting that this is indeed an effective approach to control SPP coupling within the dielectric nanoribbon waveguide.