Nonlinear optical properties of silver sols prepared by photoreduction method

The third-order nonlinear susceptibility (χ(3) of silver sol prepared by a photochemical method was measured by the degenerate four-wave mixing method. The χ(3) of the silver sol of brown-green color was larger than that of yellow-brown color. The photo-induced aggregation of silver particles affects the χ(3) of the sol. It has been found that the χ(3) of the silver sol is proportional to the intensity of surface-enhanced raman scattering from carboxylate ions adsorbed on the silver particle. The increase of χ(3) by the enhanced local electric field due to surface plasmon resonance is proposed.