Single-pulse and multi-pulse damage behaviors of "standard" (with λ/4 stack structure) and "modified" (with reduced standing-wave field) HfO<sub>2</sub>/SiO<sub>2</sub> mirror coatings are investigated using a commercial 50-fs, 800-nm Ti:sapphire laser system. Precise morphologies of damaged sites display strikingly different features when the samples are subjected to various number of incident pulses, which are explained reasonably by the standing-wave field distribution within the coatings. Meanwhile, the single-pulse laser-induced damage threshold of the "standard" mirror is improved by about 14% while suppressing the normalized electric field intensity at the outmost interface of the HfO<sub>2</sub> and SiO<sub>2</sub> layers by 37%. To discuss the damage mechanism, a theoretical model based on photoionization, avalanche ionization, and decays of electrons is adopted to simulate the evolution curves of the conduction-band electron density during pulse duration.
© 2011 Chinese Optics Letters
Shunli Chen, Yuan'an Zhao, Hongbo He, and Jianda Shao, "Effect of standing-wave field distribution on femosecond laser-induced damage of HfO2/SiO2 mirror coating," Chin. Opt. Lett. 9, 083101-083101 (2011)