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Proceedings Paper

Role of electron-phonon coupling in femtosecond laser damage of metals
Author(s): Sebastian S. Wellershoff; Jens Gudde; Julius Hohlfeld; Juergen G. Muller; Eckart Matthias
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Paper Abstract

Multishot laser damage thresholds of Au-, Ni-, Cr-, and Mo- films on fused silica have been measured with 200 fs/400 nm pulses for a sequence of film thicknesses. We found a pronounced dependence of threshold fluences on film thickness in the ranges below 50 nm for Ni and Cr, below 70 nm for Mo, and extending up to 700 nm for Au. These variations reflect the depth of hot electron diffusion which is governed by the strength of the electron-phonon coupling. The onset of damage is defined as melting for Au-, Ni- and Mo-films. For Cr-films, we could identify the brittle-to ductile phase transition as well as melting. The change of damage thresholds can be described by the two-temperature model, provided the temperature dependence of optical and thermal properties of the material is properly accounted for. By fitting model predictions to the extrapolated single-shot damage thresholds, we find the following values of electron-phonon coupling constants (in units of 1016 W/Km3): g (Au) equals 2 plus or minus 20%, g (Ni equals 36 plus or minus 40%, g (Cr) equals 42 plus or minus 40%, g (Mo) equals 13 plus or minus 40%.

Paper Details

Date Published: 14 September 1998
PDF: 10 pages
Proc. SPIE 3343, High-Power Laser Ablation, (14 September 1998); doi: 10.1117/12.321573
Show Author Affiliations
Sebastian S. Wellershoff, Freie Univ. Berlin (Germany)
Jens Gudde, Freie Univ. Berlin (Germany)
Julius Hohlfeld, Freie Univ. Berlin (Germany)
Juergen G. Muller, Freie Univ. Berlin (Germany)
Eckart Matthias, Freie Univ. Berlin (Germany)

Published in SPIE Proceedings Vol. 3343:
High-Power Laser Ablation
Claude R. Phipps, Editor(s)

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