A New Method of Surface Plasmon Excitation Mediated by Metallic Nanoparticles

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Abstract
A new method for exciting surface plasmon polaritons (SPP's) on a metal surface without using a prism coupler is experimentally tested. The method uses a layer of metallic nanoparticles placed on the metal surface. A thin layer of SiO2 containing Ag nanoparticles of average size ∼4 nm was deposited onto an Al thin film and light was incident directly onto the sample surface. The excitation of SPP's at the Al-overlayer interface was verified by the observation of a hollow light cone decoupled with the aid of a hemispherical prism, which was brought into contact with the sample. It was found that effective SPP excitation is possible when the Ag particles are placed very close to the Al surface (within ∼3 nm of the surface).