Abstract

A survey of the degenerate four-wave mixing measurements and their interpretation done on composite materials composed of nanometer coated particles, such as gold-on-aluminum, metal-on-metal, gold-on-silica, and silver-on-silica, will be presented. These data show an anomalous change in slope of the phase conjugate signal versus laser intensity from 3 to 4, depending on the thickness of the coating. To understand this feature, we study the effects of the surface properties coming from the inner surface of the particle. The effects of the second harmonic generation from such an interface, as studied, for example by Shen,¹ are investigated. The metallic part of the grain is modeled via a Kerr type nonlinearity in the dielectric constant. We obtain an expression for the dielectric constant in the effective medium theory. Using a Maxwell-Garnett and self-consistent field approximation, we then calculate the phase conjugate signal versus laser intensity to study the effect observed above.

© 1992 Optical Society of America