Dynamics of laser ablation at the early stage during and after ultrashort pulse

31st International Conference on Equations of State for Matter

Ilnitsky, D.K.^1,2 ; Khokhlov, V.A.^2 ; Zhakhovsky, V.V.^1,2 ; Petrov, Yu.V.^2 ; Migdal, K.P.^1,2 ; Inogamov, N.A.^1,2

Dukhov Research Institute of Automatics (VNIIA), Sushchevskaya 22, Moscow

127055, Russia^1

Landau Institute for Theoretical Physics, Russian Academy of Scienses, Akademika Semenova 1a, Chernogolovka, Moscow Region

142432, Russia^2

关键词: Bulk targets;    Conductive cooling;    Electron ions;    Excited electrons;    Free electron;    Hydrodynamics codes;    Material Flow;    Metallic targets;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/774/1/012101/pdf
DOI  :  10.1088/1742-6596/774/1/012101

来源: IOP

【 摘 要 】

Study of material flow in two-temperature states is needed for a fundamental understanding the physics of femtosecond laser ablation. To explore phenomena at a very early stage of laser action on a metallic target our in-house two-temperature hydrodynamics code is used here. The early stage covers duration of laser pulse with next first few picoseconds. We draw attention to the difference in behavior at this stage between the cases: (i) of an ultrathin film (thickness of order of skin depth dskinor less), (ii) thin films (thickness of a film is 4-7 of dskinfor gold), and (iii) bulk targets (more than 10dskinfor gold). We demonstrate that these differences follow from a competition among conductive cooling of laser excited electrons in a skin layer, electron-ion coupling, and hydrodynamics of unloading caused by excess of pressure of excited free electrons. Conductive cooling of the skin needs a heat sink, which is performed by the cold material outside the skin. Such sink is unavailable in the ultrathin films.