Causes of Damage in Multilayer Dielectric Coatings Exposed to High Average Power Visible Laser Radiation

Causes of damage in multilayer dielectric coatings exposed to high average power visible lasers have been examined. Damage has been seen to be related to coating defects, surface contamination, and coating absorption. Defects and contamination, particularly those larger than 4um, have been observed to significantly lower the damage threshold for high reflective coatings. Attempts have been made to visually evaluate defects and surface contamination prior to damage in order to find correlation with the damage threshold. The methods used to evaluate coating defects and conduct high average power damage testing as well as test results are presented. This work demonstrates the value of controlling sources of defects in manufacture and contamination for use in high average power visible laser systems. 7 refs., 7 figs., 4 tabs.