The effect of laser beam size on laser-induced damage performance

The influence of laser beam size on laser-induced damage performance, especially damage probability and laser-induced damage threshold (LIDT), is investigated. It is found that the damage probability is dependent on the beam size when various damage precursors with different potential behaviors are involved. This causes the damage probability and the LIDT to be different between the cases under a large-aperture beam and under a small-aperture beam. Moreover, the fluence fluctuation of large-aperture laser beam brings out hot spots, which move randomly across the beam from shot to shot. Thus it leads the most probable maximum fluence after many shots at any location on the optical component to be several times the average beam fluence. These two effects result in the difference in damage performance of the optical component between the cases under a large-aperture laser and under a small-aperture laser.