Nonlinear optical properties of multi-metal nanocomposites in a glass matrix

The lower and upper bounds for the nonlinear susceptibility of a multi-component nanocomposite composed of a glass host and nanoparticles of multiple metals are calculated within the context of the Hashin-Shtrikman formulation. We have applied this effective medium theory to the following ternary composites: AgCu:SiO₂ and AgAu:SiO₂ in the form of mixtures. These bounds were used to estimate the limits of the nonlinear effective third-order susceptibility of the composite as a function of wavelength, volume fraction and particle size. It is shown that the modulation of the third-order susceptibility of the metal by local-field enhancement due to plasmon resonance results in unexpected nonlinear responses which could be of interest to surface-enhanced Raman scattering, plasmonics and nanophotonics.