SIMULATION ON NONLINEAR OPTICAL ABSORPTION OF BINARY METALS DISPERSED(Au,Ag,Cu)/SiO_2 NANO-COMPOSITE FILMS BY MODIFIED MIE THEORY
(Au,Ag,Cu)/SiO_2二元金属单分散复合薄膜非线性光吸收性的Mie理论模拟

Due to the surface plasmon resonance (SPR) and enhanced local field effect of metal particles, nano-composite films exhibit a variety of properties, such as large third order nonlinear susceptibility, superfast response time and absorption peaks in the optical spectra at a special wavelength. Therefore they are attractive candidates for optical communication, such as information storage and optical device. In recent years, the metal nanoparticle nonlinear optical composite films have been developed rapidly, expanded from single metal nano particle dispersion system to the dual metal nano particle dispersion system. However, theoretical study on the nonlinear optical absorption of the dual metal nano particle dispersion system is quite rare. In this study, the optical absorption spectra of the (Ag, Cu)/SiO2, (Au, Cu)/SiO2 and (Ag, Au)/SiO2 binary metals dispersed nano-composite films were simulated by modified Mie theory. When the metal particles with a low full factor are smaller than the incident wavelength in diameters, the optical spectra of (Ag, Cu)/SiO2, (Au, Cu)/SiO2 and (Ag, Au)/SiO2 composite films in which the nanoparticles solely dispersed in each metal state, can be calculated and analyzed based on the modified Mie theory using the optical parameters of the component. Two SPR absorption peaks appear in the corresponding wavelength of the single metal dispersed nano-composite films. The intensities of SPR absorption peaks depend strongly on the relative content of binary metals, while their peak positions are constant regardless of the content. The calculated optical absorption spectra by proposed method in this study are in good agreement with the reported experiment results. It suggests that the linear superposition method is feasible to calculate the absorption spectra of other separated binary and/or multiplex metals dispersed nano--composite films.