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Proceedings Paper

Effect of air breakdown on short-pulsed laser drilling
Author(s): T. V. Kononenko; S. M. Klimentov; V. I. Konov; F. Dausinger
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Paper Abstract

Laser-induced air breakdown near a steel target surface ablated by short (300 ps and 10 ns) laser pulses was studied with optical emission spectroscopy to determine conditions of the breakdown ignition and time-integrated spatial localization of the laser plasma. The air breakdown was found to occur in a wide range (5-1000 mbar) of ambient air pressures, if the energy density exceeds ~10 J/cm2 for the IR radiation (λ=1078 nm) and ~40 J/cm2 for the visible light (λ=539 nm). Both the crater bottom ablation and evaporation of residual metal droplets suspended in air can ignite the low-threshold air breakdown. The experiments on deep laser drilling of steel demonstrate a sharp decrease of the drilling rate and simultaneous increase of the crater entrance diameter after the crater depth reaches a critical value. The critical crater depth increases with the applied energy density, under decrease of the ambient air pressure and under shortening of the laser pulses. The critical depth correlates with longitudinal shift of the time-integrated maximum plasma emission away from the ablated surface. Noticeable etching of the crater walls by the laser-induced plasma is observed, if movement of the plasma plume away from the ablated surface is stopped by the ambient air before the plasma leaves the crater. Interaction of the plasma with the crater walls should block ejection of the melt phase which is proposed as a reason for the observed sharp decrease of the drilling rate in a deep crater.

Paper Details

Date Published: 26 April 2006
PDF: 9 pages
Proc. SPIE 6161, International Conference on Lasers, Applications, and Technologies 2005: Laser-Assisted Micro- and Nanotechnologies, 616106 (26 April 2006); doi: 10.1117/12.675005
Show Author Affiliations
T. V. Kononenko, General Physics Institute (Russia)
S. M. Klimentov, General Physics Institute (Russia)
V. I. Konov, General Physics Institute (Russia)
F. Dausinger, Univ. of Stuttgart (Germany)

Published in SPIE Proceedings Vol. 6161:
International Conference on Lasers, Applications, and Technologies 2005: Laser-Assisted Micro- and Nanotechnologies
Vitaly I. Konov; Vladislav Ya. Panchenko; Koji Sugioka; Vadim P. Veiko, Editor(s)

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