Abstract

Observation of surface-enhanced nonlinear optical effects in silver island films traces back to the early 1980’s when surface-enhanced optical second-harmonic generation (SHG) and surface-enhanced Raman scattering where observed in the silver island films. The enhancement of the SHG intensity up to three orders of magnitude was attributed to the resonant enhancement of local field factor at the SHG wavelength mediated by local surface plasmon excitation in silver nanoparticles. Important aspect of the surface-enhanced SHG from the silver island films is the strong incoherency of the SHG radiation, which manifest itself throw the strong diffuseness and depolarization of the SHG radiation. The silver island films being 2-D random arrays of randomly shaped nanoparticles possess the spatial fluctuations of the second-order nonlinear susceptibility and local optical field factors. These result in fluctuations of quadratic nonlinear polarization, which are the sources of incoherent SHG, in other words the second-order hyper-Rayleigh scattering (HRS) at the SH wavelength. Strongly enhanced and diffuse SHG from rough silver films has been intensively studied since early 1980’s.

© 2004 Optical Society of America