A new method of surface plasmon excitation using metallic fine particles

A system consisting of Ag fine particles several nanometers in size placed on an Al surface was prepared by depositing a SiO2-Ag co-sputtered film onto a vacuum-evaporated Al thin film. The excitation of a surface plasmon polariton (SPP) mode on the Al surface was observed by the reversed attenuated total reflection (RATR method. The RATR results obtained by changing the distance of the particle from the surface demonstrate that the existence of Ag particles very close to the Al surface enables a photon to excite directly the non-radiative SPP mode. A calculation of the surface charge density on the Al surface suggests that electromagnetic normal modes, localized in the space between the Ag particles and the Al surface, play an important role in the excitation of the SPP.