Direct measurement of the femto-second laser ablation dynamics by using the single-shot soft X-ray laser interferometer

Hasegawa, Noboru; Nishikino, Masaharu; Yamagiwa, Mitsuru; Kawachi, Tetsuya; Suemoto, Toru; Tomita, Takuro*; Baba, Motoyoshi*; Terakawa, Kota*; Minami, Yasuo*; Takei, Ryota*

The dynamical processes of the laser-induced surface modifications such as laser ablation come to attract much attention for the micro processing by the ultra-short laser pulse. The soft X-ray laser (SXRL) is suitable for probing the initial process of the surface morphological changes, because it has the suitable wavelength (= 13.9 nm, penetration depth = 5 nm), short duration (= 7 ps) and large photon numbers (larger than 1e+10 photons/shot). In this study, we have developed the femto-second laser pump and soft X-ray laser probe system with the soft X-ray interferometer in order to observe the dynamical processes of the femto-second laser ablation. By using this system, we succeed to obtain the temporal evolution of the laser induced Pt surface. From this result, it was revealed that the expansion speed of the ablation front at the center (= 1500 m/s) of the ablation area in the initial stage of the ablation process.