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Single-pulse and multi-pulse damage behaviors of “standard”(with λ/4 stack structure) and “modified”(with reduced standing-wave field) HfO2/SiO2 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 HfO2 and SiO2 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.
Single-pulse and multi-pulse damage behaviors of “standard ” with λ / 4 stack structure and “modified ” with reduced standing-wave field HfO2 / SiO2 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 numbers 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 HfO2 and SiO2 layers by 37% .To discuss the damage mechanism, a theoretical model based on photoionization, avalanche ionization, and decays of electrons are adapted to simulate the evolution curves of the conduction-band electron density during pulse duration.