Non-phase-matched optical third-harmonic generation in noncentrosymmetric media: Cascaded second-order contributions for the calibration of third-order nonlinearities

Cascaded second-order contributions to third-harmonic generation are analyzed in detail, and are exploited to obtain reliable reference values for third-order nonlinear optical susceptibilities at several wavelengths. We describe the influence of boundary conditions on the measured properties for the case of high nonlinearity crystals such as KNbO3 and the organic salt 4-N, N-dimethylamino-4'-N'-methylstilbazolium toluene-p-sulfonate (DAST). Wavelength dispersion relations for the electronic third-order susceptibilities derived from third-harmonic generation experiments are discussed. Our reference standards allow a comparison of the third-harmonic generation results with measurements of the Kerr susceptibility determined with degenerate four-wave mixing and the z-scan technique and shows that chi((3))(-omega,omega,-omega,omega)greater than or equal to chi((3))(-3 omega,omega,omega,omega) in the investigated wavelength range. The investigation of structure-property relationships between the perovskite crystals KNbO3 and KTaO3 indicates similar bond nonlinearities in these two compounds.