A Study of the femto-second laser ablation process in metals by using a soft X-ray laser probe

Hasegawa, Noboru; Nishikino, Masaharu; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Tomita, Takuro*; Suemoto, Toru; Onishi, Naofumi*; Ito, Atsushi*; Baba, Motoyoshi*; Minami, Yasuo*

We have succeeded in simultaneous observation of temporal evolution of two different surfaces of the femto-second laser ablation process of metals (Au) by using the soft X-ray laser probe. The ablation front with a solid or the liquid surface and the expansion front with thin film structure were observed from the results of the soft X-ray interferogram, reflective imaging and shadowgraph. The expansion front separated from the ablation front was thin, dense and smooth so as to work as the beam splitter for the soft X-rays at the time within 1 ns after the laser irradiation. The expansion front that included almost all of the mass of the crater inside was kept at the time around 1 microsecond, and the height of that reached over 100 micron. From these results, the ablation front gradually becomes vapor while maintaining a clear and smooth expansion front.