We report a theoretical study of the Z-scan technique by using quasi-one-dimensional slit beams for characterizing third-order optical nonlinearity. We verify that the sensitivity of this Z-scan scheme is roughly the same level as top-hat beams and is greatly higher than Gaussian beams by a factor of approximately 2.5. This scheme should have the capability to measure less than a λ/500 wave-front distortion at least. Numerical formulas obtained in theory allow direct estimation of nonlinear refraction and absorption coefficients from the normalized peak–valley transmittance difference measured. Some salient features are also discussed. This Z-scan scheme is also demonstrated experimentally.
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