Sol-gel processing and optical nonlinearity of gold colloid-doped silica glass

Abstract

Au microcrystal-doped glass films with high optical nonlinearity were prepared by the sol-gel method with dip-coating using NaAuCl4·2H2O and tetraethyl orthosilicate (TEOS) as starting materials. The glass film with an Au/Si atomic ratio of 0.01 was successfully prepared. The nonlinear susceptibility χ(3) of the film was 7.7 × 10-9 esu. Microcrystals with a radius of about 7A and of about 30A coexisted in the glass film. The nonlinear susceptibility of Au microcrystals itself in the film, χm(2), was 1.0 × 10-7 esu and was two times larger than that observed in Au-doped glasses prepared by the melting method. Subsequent heat treatment of the films at 1000°C changed the absorption spectra and decreased χ(3) by a factor of two. The atomic ratio of Au/Si was able to be increased to 0.04.