A study of the thermal-induced nonlinearity of Au and Ag colloids prepared by the chemical reaction method

The nonlinear optical properties of metal Au and Ag colloidal solutions prepared by the chemical reaction method were investigated by a single beam Z-scan technique. Under CW 633 nm excitation, the Au and Ag colloidal solutions exhibited a large thermal-induced refractive index n2. At the same time, the thermo-optic coefficients dn/dT of the Au and Ag colloidal solutions were obtained. The mechanism responsible for the process of nonlinear refraction was discussed in term of laser heating effect.