Mechanisms of ablation-rate decrease in multiple-pulse laser ablation |
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Authors: | EG Gamaly AV Rode A Perrone A Zocco |
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Institution: | (1) Research School of Physical Science and Engineering, Australian National University, Canberra, ACT 0200, Australia, AU;(2) Lecce University, Physics Department, Instituto Nazionale Fisica della Materia, PO Box 193, 73100 Lecce, Italy, IT |
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Abstract: | We present two sets of experimental results on the ablation-rate decrease with increase of the number of consecutive laser
pulses hitting the same spot on the target surface. We have studied laser ablation of a carbon target with nanosecond pulses
in two different interaction regimes: one with a XeCl laser (λ=308 nm) and the other with a Nd:YAG laser (λ=1064 nm), in both
cases at the intensity ∼5×108 W/cm2 Two different mechanisms were found to be responsible for the ablation-rate decrease; they are directly related to the two
different laser–matter interaction regimes. The UV-laser interaction is in the regime of transparent vapour (surface absorption).
The increase of the neutral vapour density in the crater produced by the preceding laser pulses is the main reason for the
decrease of ablation rate. With the IR laser each single laser pulse interacts with a partially ionised plume. With increase
of the number of pulses hitting the same spot on the target surface, the laser–matter interaction regime gradually changes
from the near-surface absorption to the volume absorption, resulting in the decrease in absorption in the target and thus
in the decrease in the ablation rate. The change in the evaporation rate was considered for both vacuum and reactive-gas environments.
Received: 21 February 2001 / Accepted: 26 February 2001 / Published online: 23 May 2001 |
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Keywords: | PACS: 52 38 Mf |
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