A new technique for measuring third-order susceptibility with a Mach–Zehnder interferometer with a pump–probe system is proposed. The optical setup is combined with a charge-coupled device for image processing. With the proposed method it is possible to resolve the spatial profile of a complex nonlinear variation index with only one laser shot in the nonlinear material. Therefore we can get intensity-resolved information by comparing this profile, pixel per pixel, with that of the incident beam. To verify the validity of the method, we carry out measurements of reference materials illuminated by linearly polarized light. Good agreement is obtained with measurements made by various authors. An advantage of this new technique is that only one laser shot is needed to minimize the risk of damage in fragile nonlinear materials.
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