The scattering of surface plasmon polariton (SPP) waves can be manipulated by various plasmonic structures. The plasmonic structure composed of arranged subwavelength nanobumps on a gold thin film is the promising structure to manipulation SPP wave. By controlling the geometric shape of the structures, the height, position, and pattern of scattered light from SPP wave can be modulated as desired. A clear single focusing spot can be reconstructed at a specific altitude by a particular curved structure with appropriate curvature and adjacent interspacing of nanobumps. The designed light patterns reconstructed by the focusing spot from the arranged curved structures at a specific observation plane are clearly demonstrated.
Dipole and quadrupole surface plasmon polariton (LSPP) resonances of gold nanoparticle array were directly
investigated by a near-field scanning optical microscope (NSOM) in the fiber-collection mode. Separated gold
nanoparticles on the quartz substrate were fabricated by nanosphere lithography. Results demonstrate that controlling the
incident polarization and angle of oblique incidence enables to excite dipolar and quadrupolar LSPP at 633- and 488-nm
excitations. This observation facilitates the understanding of LSPP and interactions with nanostructures in the near field
that can be used as a guideline for fabricating nanostructures in controlling spatial distributions of LSPP for ultra
sensitive bio-/chemo-detectors or plasmonic metamaterials.
The near-field distribution of plasmonic coupling effect in gold nanoparticle pairs was directly investigated by a nearfield
scanning optical microscope (NSOM) in the fiber-collection mode. NOSM images show that the localized
plasmonic coupling and the electromagnetic field distribution of nanoparticle pairs are systematically influenced by the
interparticle space and axial direction of incident polarization. This observation can facilitate the understanding of
localized hot spots in surface-enhanced Raman spectroscopy in the near field and can be used as a guideline for
fabricating specific nanostructures in controlling the spatial distribution of surface plasmon (SP) modes for ultrasensitive
sensors or photonic devices.
Surface plasmon-like (SPL) modes are the electromagnetic surface eigenmodes on structured perfect-conductor
surfaces. The standard eigenvalue-solving method is adopted to solve these modes. The fields of the SPL
modes are maximal on the conductor surface and decay exponentially into both the air and the structured
conductor. On thin structured conductors, the SPL mode splits into a high-frequency anti-symmetric mode and
a low-frequency symmetric mode. The SPL modes are slow-wave modes with the frequencies that approach an
equivalent surface-plasmon frequency at large in-plane wavevectors. However, the interhole interaction
prevents the dispersion relation from being generally described by an analytic equation.
The phenomenon of resonant tunneling through thin metal films with periodic narrow grooves is attributed to excitation of the surface plasmon (SP) via the periodic groove structure coupler at the metal surface. In this paper, we will use the particle-in-cell (PIC) plasma simulation method to study this SP-mediated optical tunneling. The PIC method is a time-domain scheme to calculate self-consistently the interaction between the electromagnetic fields and the plasma particles. At the beginning of simulation, the mobile electrons and immobile positive ions are uniformly distributed in the thin Gaussian-shaped-grooved silver film with the plasma density calculated from silver's plasma frequency. The momentum collision-frequency method is employed to model the collision dissipation. For normally incident TM-polarized wave, the transmission coefficients have the maximum values at the LSP resonant modes, similar to the results predicted by Drude model, except for with lower transmission coefficients. Due to the electron dynamics considered in the PIC method, the plasma energy and the trajectories can be monitored during the simulation. The change of the averaged plasma energy with time exhibits some ripple-like patterns, which comes from various competing processes of heating and cooling. But the temperature of the plasma has little effect on the transmission coefficient and the wave tunneling.