Mechanism of femtosecond laser nano-ablation for metals

Miyasaka, Y.; Institute For Chemical Research, Kyoto University, Gokasho, Uji, 611-0011, Japan Department Of Physics, Kyoto University, Kitashirakawa, Sakyo, 606-7501, Japan, Sakagami, H.; Department Of Physics, Nagoya University, Nagoya, Aichi, 464-8602, Japan National Institute For Fusion Science, Toki-City, Gifu, 509-5292, Japan, Sakabe, S.; Institute For Chemical Research, Kyoto University, Gokasho, Uji, 611-0011, Japan Department Of Physics, Kyoto University, Kitashirakawa, Sakyo, 606-7501, Japan, Hashida, M.; Institute For Chemical Research, Kyoto University, Gokasho, Uji, 611-0011, Japan Department Of Physics, Kyoto University, Kitashirakawa, Sakyo, 606-7501, Japan, Tokita, S.; Institute For Chemical Research, Kyoto University, Gokasho, Uji, 611-0011, Japan Department Of Physics, Kyoto University, Kitashirakawa, Sakyo, 606-7501, Japan, Shimizu, M.; Institute For Chemical Research, Kyoto University, Gokasho, Uji, 611-0011, Japan Department Of Physics, Kyoto University, Kitashirakawa, Sakyo, 606-7501, Japan & Ogata, T.; Department Of Physics, Nagoya University, Nagoya, Aichi, 464-8602, Japan
Metals have three ablation threshold fluences (high,middle and low-threshold fluence, here called) forfemtosecond laser pulses. In order to investigatethe physics of metal ablation under an intenseoptical field, the ions emitted from a laserirradiatedcopper surface were studied by time-offlightenergy spectroscopy. The low laser fluenceat which ions are emitted, Fth,L is 0.028 J/cm2, andtwo higher emission thresholds were identified atfluences of Fth,M =0.195 J/cm2 and Fth,H =0.470J/cm2. The relation between the number of emittedions per pulse Ni...