Damage Control:

James Doty

Thanks to modern manufacturing practices, thin-film coatings for high-power laser systems can withstand high fluences before experiencing catastrophic damage. Yet laser fluence all too often damages optics in real-world applications. End users often assume that the coatings are to blame, but this is rarely the case.

Two common sources of coating damage for high-energy pulsed lasers in the visible and near-infrared ranges are external contamination and "hot spots" in the laser's beam structure. External contamination includes discrete absorption sites such as lint, dust or a material nodule (commonly referred to as spit); and diffuse contamination from gaseous or molecular sources...