Fast nonlinearity of the refractive index of solid-state dielectric active media

Research on the nonlinear refractive indices of solid dielectric active media is reviewed. The review is restricted to media for which the nonlinear refractive index is fast, i.e., has a relaxation time ? < 10?9 s. The nature of the nonlinear refractive index, its relaxation time, and its dispersion are discussed. Measurements of the parameters of the nonlinear refractive index of more than 160 laser and optical glasses and crystals are collected.