Components of the third-order nonlinear susceptibility tensors in KDP, DKDP and LiNbO3 nonlinear optical crystals

The ratio of the components of the third order nonlinear susceptibility tensors (which are responsible for the self-action effects) in KDP, DKDP and LiNbO₃ crystals is measured at the 1064-nm wavelength of a Nd:YAG laser. Measurements were made on the basis of analysis of polarisation dependences of the focused radiation transmission by the z-scan method. The obtained polarisation dependences of the effective Kerr nonlinearity correspond to a tensor of the fourth rank that is symmetric in all its indices. The measured values of the Kerr nonlinearities that are responsible for the self-action of o-polarised radiation were found to be (1.75 ± 0.55) × 10^-14 and (2.4 ± 0.8) × 10^-13 esu for KDP and LiNbO₃ crystals, respectively.