Interaction Between Localized And Propagating Surface-Plasmons - Ag Fine Particles On Al Surface

Samples consisting of Ag fine particles of 4 nm in size placed near to an Al surface were prepared by depositing Ag-SiO2 composite films by an r.f. cosputtering method onto vacuum-evaporated Al films. Angle-scan attenuated total reflection (ATR) measurements were performed over a wide wavelength range (lambda = 350-630nm) covering the resonance region (lambda similar to 410 nm) of localized surface plasmon (LSP) in the Ag particles. It was found that the existence of Ag fine particles near to the Al surface led to a deformation of the dispersion curve of the surface plasmon polariton (SPP) propagating on the Al surface, in particular, in the LSP resonance region. A pronounced increase in the SPP damping in the LSP resonance region was also observed. The interaction between LSP and SPP was found to become much stronger as the distance between the particles and the surface decreased.