Application of the Z-scan technique to a saturable photorefractive medium

Summary form only given. The Z-scan technique is an extensively utilized experimental technique for studying optical nonlinearities in a wide class of photorefractive media. In this work we derive formulas for the generalized three-level scheme, describing the refractive index change under the absorption saturation, and exploit these for modifying the formulas for the Z-scan technique. We apply the developed model for accurate determination of the refractive index change and the nonlinear index of refraction from the experimental Z-scans obtained for polymer films containing bR and Langmuir-Blodgett films of porphyrin, and compare these values with the data obtained by other methods.