Method for studying laser-induced damage from sparse defects

Laser damage testing is widely utilized by laser and laser system builders to ensure the reliability of their products. When damage is due primarily to sparse defects, the relatively limited data sets acquired under typical testing protocols tend to imply that laser damage probabilities go to zero below some reported damage threshold. However, this is rarely an accurate picture of the actual damage characteristics of the sample set. This study attempts to establish a correlation between observed coating defects and laser damage (from a 1064 nm laser in the nanosecond regime), utilizing a large sample size from a single coating run, together with the actual fluence levels present at the defect sites. This correlation is then used to predict damage for optics coated under different circumstances. Results indicate that it might be possible to develop an alternate methodology for determining damage characteristics, based on observed defects, which is both more reliable and less time-consuming than traditional laser damage testing.