Sol-Gel Processing and Optical Nonlinearity of Gold Colloid-Doped Silica Glass

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 7.7×10-9esu. Microcrystals with a radius of about 7Å and of about 30Å coexisted in the glass film. The nonlinear susceptibility of Au microcrystals itself in the film, χm(3), was 1.0×10-7esu 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.