Annealing effects on microstructure and laser-induced damage threshold of HfO_2/SiO_2 multilayer mirrors

with annealing up to 400°C. The improvement of LIDT with annealing is explained through oxygen vacancy defects as well as grain-size-dependent thermal conductivity. Finally, the observed laser damage morphology, such as circular scalds and ablated multilayer stacks with terrace structure, are analyzed.