Nonlinear Optical and Laser Damage Properties of KDP Crystal with Trace Impurities in Bulk

Abstract

AbstractSmall‐sized potassium dihydrogen phosphate (KDP) samples cut from the pyramid sector of a large KDP boule are observed to have different impurity content. The nonlinear absorption properties of two KDP samples containing different impurities are characterized by Z‐scan technique with picosecond laser at 355 nm wavelength. Reverse saturable absorption effects are found in samples, with nonlinear absorption coefficients of 7.35 × 10−2 cm GW−1 and 15.91 × 10−2 cm GW−1. The sample with more impurity contents exhibits stronger nonlinear absorption. Such behavior is considered to be a result of nonlinear energy coupling under 355 nm laser irradiation assisted by impurity defects. Nanosecond laser‐induced damage test at 355 nm of the two KDP samples is further investigated. The bulk damage thresholds of the two samples are 4.7 and 0.423 J cm−2 respectively, indicating that impurity‐induced nonlinear absorption might play an important role in laser‐induced damage processes.