A nodule dome removal strategy to improve the laser-induced damage threshold of coatings

Various coatings in high-power laser facilities suffer from laser damage due to nodule defects. We propose a nodule dome removal (NDR) strategy to eliminate unwanted localized E-field enhancement caused by nodule defects, thereby improving the LIDT of laser coatings. It is theoretically demonstrated that the proposed NDR strategy can reduce the localized E-field enhancement of nodules in mirror coatings, polarizer coatings, and beam splitter coatings. A UV mirror coating is experimentally demonstrated using the NDR strategy. The LIDT is improved to about 1.9 and 2.2 times for the UV mirror coating without artificial nodules and the UV mirror coating with artificial nodule seeds with a diameter of 1000 nm, respectively. The NDR strategy, applicable to coatings prepared by different deposition methods, improves the LIDT of laser coating without affecting other properties such as spectrum, stress, and surface roughness, indicating its broad applicability in high-LIDT laser coatings.