Effect of thermal annealing on laser damage resistance of KDP at 3ω

In order to characterize the effect of thermal annealing on laser damage resistance of KDP, several combinations of laser conditioning and thermal annealing were applied to two SHG KDP samples. One sample was tested at 3ω, 16ns and the other one at 3ω, 2.5ns. Results show that whereas thermal annealing improves laser damage for a 16ns pulse, no effect can be measured at a pulse length of 2.5ns. Combining laser conditioning and thermal annealing has a stronger effect on laser damage resistance than laser conditioning alone, even for a 2.5ns pulse length for which thermal annealing was found to have little or no influence. It was also found that for a short pulse length maximum gain was obtained when thermal annealing was applied after laser conditioning.