Measurements of the tensor properties of third-order nonlinearities in wide-gap semiconductors

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Abstract
We extend the z-scan technique to provide for measurements of the sign and the magnitude of all the independent components of χ(3) for isotropic and cubic-symmetry materials. This technique is used to measure the dispersion of the tensor components of the real and the imaginary parts of χ(3) for various wide-gap semiconductor materials by use of femtosecond laser pulses. Our measurements of the polarization dichroism of the nonlinear-index and two-photon absorption coefficients are in fair agreement with recent theoretical calculations; however, substantial discrepancies exist between the measured and predicted values for the corresponding anisotropy parameters.