Accumulation effect of multi-shot laser-induced damage to optical coatings

The accumulation effect of multi-shot laser-induced damage to optical coatings was investigated. Laser damage testing was performed at 1 064 nm with nanosecond pulses at a pulse length of 12 ns, using an accurate and reliable measurement system. The damage threshold and the number of shots were studied by a statistical method. Compared with the case of single shot laser damage, it is concluded that the microdefects in the optical coatings are responsible for the multiple-pulse damage to mirrors. The damage mechanism can be used to explain the damage process. The expressions for the damage threshold and the number of shots are founded. Nomarski microscope was employed to observe the laser-induced damage morphology after laser irradiation．