title: Impact of substrate pits on laser-induced damage performance of 1064-nm high-reflective coatings.
abstract: The laser damage resistance of coatings in high-power laser systems depends significantly on the surface quality of the substrate. In our experiment, pits were precisely fabricated on the surface of fused silica substrate using a femtosecond laser processing bench. The HfO2/SiO2high-reflective coatings at 1064 nm were deposited by conventional e-beam evaporation onto fused silica substrates with and without pits, respectively. The internal crack that was induced by the substrate geometrical structure was first observed in our experiment. The laser-induced damage threshold test showed negative effects of the substrate pits on the laser resistance of high-reflective coatings. Simulations by the finite element method were carried out, and results demonstrated that the modulation of a high reflector multilayer geometry could lead to electrical-field amplification and reduce laser damage resistance. Combined with its poor mechanical properties, the pits on substrate could contribute to the occurrence of damages.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Chai
authors.forename: Meiping
authors.initials: M
authors.lastname: Zhu
authors.forename: Zhengyuan
authors.initials: Z
authors.lastname: Bai
authors.forename: Kui
authors.initials: K
authors.lastname: Yi
authors.forename: Hu
authors.initials: H
authors.lastname: Wang
authors.forename: Yun
authors.initials: Y
authors.lastname: Cui
authors.forename: Jianda
authors.initials: J
authors.lastname: Shao