Saturation of the all-optical Kerr effect in solids

We discuss the influence of the higher-order Kerr effect (HOKE) in wide band gap solids at extreme intensities below the onset of optically induced damage. Using different theo- retical models, we employ multiphoton absorption rates to compute the nonlinear refractive index by a Kramers-Kronig transform. Within this theoretical framework we provide an esti- mate for the appearance of significant deviations from the standard optical Kerr effect pre- dicting a linear index change with intensity. We discuss the role of the observed saturation behavior in practically relevant situations, including Kerr lens mode-locking and supercon- tinuum generation in photonic crystal fibers. Furthermore we present experimental data from a multi-wave mixing experiment in BaF2 which can be explained by the appearance of the HOKE