Nonlinear refractive-index measurements of glasses using three-wave frequency mixing

We have developed a rapid and accurate method for measuring the nonlinear refractive index of transparent materials. It is based on a version of three-wave mixing in which the frequencies of the two input beams are adjusted to differ by about 60 cm−1. The nonlinear index of a material is measured relative to that of a standard with a known index. Our measurements of 27 glasses are in good agreement with previous results, where available, and with the n2 values calculated empirically from linear index parameters. We also discuss the relationship between the observed nonlinear index and the structure and composition of the glasses.