Observation of low ablation threshold of materials irradiated by pico-second EUV laser pulse

Kawachi, Tetsuya; Faenov, A.*; Tanaka, Momoko; Ishino, Masahiko; Pikuz, T.*; Hasegawa, Noboru; Bulanov, S. V.; Inogamov, N. A.*; Khokhlov, V.*; Anisimov, S. I.*

We have observed ablation threshold of materials irradiated by pico-second EUV laser pulse. The obtained ablation threshold was lower by 2-3 orders of magnitude than the cases irradiated by visible or infrared laser pulse. In order to explain the present result, we have performed computer simulation involving molecure-dynamics and hydro-dynamics. The results shows that in the case of EUV laser irradiation, high temperature and high pressure region is generated in the localized area of the materials and following generation of the strong tenssile induces spallative destruction of the material. This mechanism is completely different from the case by use of visible or infrared laser pulse.