Laser-induced Damage Probability at 1.06 microm and 0.69 microm.

The first directly comparable measurements of the laser-induced surface damage process at both ruby and Nd:YAG laser wavelengths are reported. The most striking feature of the data is that all the materials studied are harder to damage at 0.69 microm than at 1.06 microm. The probabilistic nature of the laser-induced damage process at 1.06 microm was explored further by measuring the distribution of breakdown starting times with an image-converter streak camera. The observed distribution is described by the compound probability that breakdown occurs at a particular time, given that it has not occurred before that time. In addition, several connections between the probabilistic and thresholdlike interpretations of laser-induced damage are discussed. It is shown that these points of view are not totally incompatible.