BOUND ELECTRONIC KERR-EFFECT AND SELF-FOCUSING INDUCED DAMAGE IN 2ND-HARMONIC-GENERATION CRYSTALS

We present an investigation of third-order electronic nonlinearities i n second-harmonic-generation (SHG) crystals using a picosecond 532 nm wavelength beam. The crystals studied include KTP, KTA, BBO, LBO and L iNbO3. Using the Z-scan technique the nonlinear refractive indexes and two-photon absorption coefficients in the z-cut crystals are measured . as well as in KTP, BBO and LBO along the phase-matching angles for t he SHG of 1064 nm radiation. The microscopic origin of the measured re fractive nonlinearity can be understood in terms of bound electronic e ffects, and the theoretical predictions are in agreement with our meas urements. Finally, we perform an experimental study on the self-focusi ng induced damage in these crystals by extending the Z-scan method. Th e measured damage threshold is inversely proportional to the nonlinear refractive index and the thickness of a crystal. (C) 1997 Elsevier Sc ience B.V.