Tunable Multi-Port Surface Plasmon Polariton Excitation with Nanostructures

Surface plasmon polaritons (SPPs) have appealing features such as tighter spatial confinement and higher local field intensity. Manipulation of surface plasmon polaritons on metal/dielectric interface is an important aspect in the achievement of integrated plasmonic circuit beyond the diffraction limit. Here, we introduce a design of pin cushion structure and a holographic groove pattern structure for tunable multi-port SPPs excitation and focusing. Free space light is coupled into SPPs through momentum matching conditions. Both nanostructures are capable of tunably controlling of SPPs depending on the incident polarizations, while the holographic method provides more flexibility of wavelength-dependent excitations. Furthermore, a quantitative method is applied to calculate the efficiencies of excitation for both nanostructures under different conditions, including radially polarized incident beams. These results can work as a guidance and be helpful to further choice of the suitable design strategies for variable plasmonic applications such as beam splitter, on-chip spectroscopy, and plasmonic detectors.