title: Modeling the effect of nanosecond laser conditioning on the femtosecond laser-induced damage of optical films.
abstract: The effect of nanosecond laser conditioning on the femtosecond laser-induced damage behaviors of Al2O3, HfO2, SiO2single layers and Al2O3/SiO2high reflectors (HR) are explored. During femtosecond laser damage test, negative effects on enhancing the femtosecond laser-induced damage threshold (LIDT) of optical films after the nanosecond laser conditioning is found, which is opposite to the LIDT improvement in the nanosecond range. To explain the mechanism after nanosecond laser conditioning, a theoretical model including multiphoton ionization (MPI), avalanche ionization (AI) and decays of electrons with one defect state is built to simulate the evolution of electron density in the conduction band. A permanent mid-gap defect state resulting from the process of laser conditioning is introduced in our model, which is found to contribute seed electrons to conduction band and hence accelerate the final breakdown. Both the experimental result and theoretical calculation agree very well with each other.
authors.forename: Zehan
authors.initials: Z
authors.lastname: Li
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.forename: Yuanan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Yueliang
authors.initials: Y
authors.lastname: Wang
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Leng
authors.forename: Jianda
authors.initials: J
authors.lastname: Shao