Measurement of the nonlinear refractive index in optical thin films

Based on the z-scan method, an interferometric set-up for measuring the optical Kerr-effect was engineered and optimized. Utilizing a Mach-Zehnder configuration, the wave front deformation caused by the Kerr induced selffocusing is monitored. Fitting this deformation to a theoretical approach basing on a beam propagation model, the nonlinear refractive index is obtained. The procedure can be applied to measure the nonlinear refractive index of both, the substrate material as well as the deposited dielectric layer on top of the substrate. The nonlinear refractive index of a layer specially deposited for this purpose as well as for several substrate materials was measured and the results presented. © 2017 SPIE.