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Medientyp:
E-Artikel
Titel:
Femtosecond laser plasma plume characteristics in the nanojoule ablation regime
Beteiligte:
Banerjee, S. P.;
Chen, Zhijiang;
Fedosejevs, R.
Erschienen:
AIP Publishing, 2013
Erschienen in:
Journal of Applied Physics, 113 (2013) 18
Sprache:
Englisch
DOI:
10.1063/1.4804329
ISSN:
0021-8979;
1089-7550
Entstehung:
Anmerkungen:
Beschreibung:
Laser ablation of chromium with nanojoule energy UV femtosecond pulses under background pressure conditions between 0.3 Torr and 700 Torr is studied and the corresponding plasma plume images at different times after irradiation are measured. The ablation focal spot is less than or the order of a micron when 170 nJ of laser pulse energy is used. This low pulse energy leads to short lifetimes of the plasma of the order of tens of nanoseconds. The plume shape changes with ambient pressure due to the collision with background gas. An axially stretched plume changes to a more circular plume as the pressure increases. In addition, a separation of the ionic and atomic components is observed at lower pressure. These two components move at significantly different velocities as well. The plasma plume expands at almost constant velocity at very low pressure but exhibits significant deceleration at higher pressure reaching an asymptotic stopping distance. Plume images are also obtained near the ablation threshold pulse energy. The plume characteristics are compared to different models of plume expansion.