Effects of excimer laser irradiation on the KDP crystal

The progress in the development of powerful solid state lasers depends to a great extent on the laser damage threshold of KDP single crystal used for harmonics generation of laser radiation. However, the bulk damage; threshold of crystal is low. In order to condition KDP crystal, the effects of laser pre-irradiation on the KDP crystals were investigated in this paper. The KDP crystals were irradiated by excimer laser with 308-nm wavelength 35 ns pulsewidth, and we observed that the 215 nn absorption band disappeared, which is correlated with the electronic center charged oxygen vacancy. It is shown that P+ and K+ ions shifting became slow after excimer laser pre-irradiation by means of the electron probe measurement, which further demonstrated the electronic defects to be repaired. In addition, a single mode Nd-YAG laser with 10 ns pulsewidth was used in the laser damage experiments. Damage thresholds of the KDP crystals increase by a factor of 2-3.