Optical emission from surface waves supported in thin metal films

This thesis describes an experimental investigation of the properties of the surface plasmon modes supported by several thin-metal-film geometries. Surface plasmons can be thought of as TM (transverse magnetic) polarized electromagnetic waves associated with one or both of the surfaces of a thin metal film. The experimental investigation of surface plasmon phenomena in thin metal films has, for the most part, been restricted to optical absorption experiments at the Helium-Neon laser wavelength ;Corrugated thin silver film samples were fabricated and characterized by the degree of refractive index asymmetry of the dielectric media surrounding the metal film. Light emission from highly asymmetric samples was found to exhibit direct evidence for both grating-induced cross coupling as well as intrinsic coupling between surface plasmons localized at opposite metal/dielectric interfaces. In the symmetric geometry, the first observation of optical emission resulting from the decay of both long and short-range coupled surface plasmons is reported. Experimental dispersion curves for both coupled surface plasmons spanning most of the visible and part of the infrared are constructed. Also, second order Bragg scattering was observed which implied the suppression of spontaneous emission from molecules. In the slightly asymmetric case, the construction of experimental dispersion curves exhibited evidence for the evolution of surface plasmon-surface plasmon coupling into surface plasmon-waveguide mode coupling as the refractive index asymmetry of samples was gradually increased. Also, evidence of a third thin metal film excitation was found.