Saturation of the nonlinear index of refraction in semiconductor-doped glass

Interferometric measurements of saturation of the nonlinear index of refraction in a semiconductor-doped glass (Schott OG 550) are reported. The index change, measured at a wavelength of 532 nm, reaches a maximum value of ~1.5 × 10−4 at high intensity. It is shown that the magnitude of the corresponding third-order susceptibility, χ(3), is determined mainly by the absorption change. Furthermore, the effective nonlinearity is dramatically reduced by the darkening effect when the glass is exposed to an intense laser beam.