Characterization of optical performance and defect structures in nonlinear crystals for large aperture lasers

Summary form only given. Crystals of KDP and DKDP with dimensions of 41/spl times/41/spl times/1 cm/sup 3/ will be used as Pockels cell and harmonic conversion elements in the world´s largest laser system, the National Ignition Facility (NIF). Determining the optical performance of these crystals under NIF-like conditions and understanding the connection between optical performance and internal defect structure has been a crucial part of the effort to build this facility. The crystals must exhibit a high degree of optical homogeneity, low anomalous birefringence, low absorption, uniform phase matching and high laser damage threshold at the 1st, 2nd and 3rd harmonics of Nd:YAG in order to meet the NIF goals for conversion efficiency, energy on target and beam focusability. Here we review the results of extensive spectroscopy, interferometry, polarimetry, X-ray topography, phase matching homogeneity and laser-induced damage measurements on full-scale and/or sub-scale crystals.