Nonlinear behavior of laser-induced damage in KDP and DKDP under multi-wavelength irradiation

摘要

The damage performance of potassium dihydrogen phosphate (KDP, and its deuterated analog DKDP) crystals under multi-wavelength, simultaneous exposure to the harmonics of a nanosecond Nd:YAG laser system is of particular interest because it approximates the conditions taking place during frequency conversion. In this work, damage initiation under simultaneous exposure to two pulses at different wavelengths is investigated as a function of fluence in both KDP and DKDP. We have developed a novel damage testing instrumentation which allows us to measure the damage pinpoint density as a function of laser parameters, including wavelength, fluence, and pulse-length. This new method enables us to carefully quantify the damage effects of both, single-wavelength and dual-wavelength pulsed irradiation. In the latter case, we measure the laser-induced damage behavior when the fluence at one wavelength is varied while the fluence of the second wavelength is kept constant. Our results suggest that the behavior of laser-induced damage initiation under simultaneous multi-wavelength irradiation is complex and crystal dependent.