Nanosecond laser-induced damage of nodular defects in dielectric multilayer mirrors [invited]

Our recent studies on nodular damage in dielectric multilayer mirrors were first reviewed, and the main findings are taken as a foundation to further investigate the influence of seed absorptivity and asymmetrical boundary on the laser-induced damage of nodules. Experimental results showed that the seed absorptivity had a big influence on laser-induced damage thresholds (LIDTs) of the prepared nodules. A direct link between the cross-sectional |E|2 distributions and damage morphologies of nodules was found, which can perfectly explain the observed dependence of LIDTs on seed absorptivity. Another series of asymmetrical nodules were also studied in this work. The measured LIDTs of asymmetrical nodules were about 40%-70% lower than the LIDTs of the symmetrical nodules initiating from the same-sized SiO2 seeds. The weaker mechanical stability and the nonuniform |E|2 distributions are two main reasons for the lower laser damage resistance of the asymmetrical nodules.