Ultrasound generated by a femtosecond and a picosecond laser pulse near the ablation threshold

Journal Article · Mon Aug 01 04:00:00 EDT 2005 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.1999827· OSTI ID:20714007

Hebert, H; Vidal, F; Martin, F; Kieffer, J -C; Nadeau, A; Johnston, T W; Blouin, A; Moreau, A; Monchalin, J -P ^[1]

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1. Institut National de la Recherche Scientifique-Energie, Materiaux et Telecommunications, Universite du Quebec, 1650 boul. Lionel-Boulet, Varennes, Quebec, J3X 1S2 (Canada)

We have investigated high-frequency ultrasound generated by single laser pulses in thin (50 {mu}m) aluminum foils as a function of the laser fluence. Laser-pulse durations of 80 fs and 270 ps were used to compare the ultrasound generated in two very different regimes: thermoelastic and ablation. The measured rear-surface displacement induced by the ultrasound pulse is similar after 50-{mu}m propagation through the foils for the two laser-pulse durations in the fluence range of 0.1-0.7 J/cm{sup 2}. For fluences greater than the ablation threshold (0.25 and 0.63 J/cm{sup 2} for the 80-fs and 270-ps pulses, respectively), the ultrasound amplitude generated by the 270-ps laser pulse is increased significantly due to absorption of laser energy by the ablating plasma. This is not observed for the 80-fs laser pulse since ablation is produced well after the laser-pulse irradiation of the target. The measured surface displacement as a function of laser fluence is compared to the calculations of a one-dimensional fluid code for both laser-pulse durations. The model calculations agree in many ways with the experimental results, but some discrepancies are observed.

• OSTI ID: 20714007
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 3 Vol. 98; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABLATION
ABSORPTION
ALUMINIUM
AMPLITUDES
FLUIDS
FOILS
LASERS
LIGHT TRANSMISSION
ONE-DIMENSIONAL CALCULATIONS
PLASMA
PULSED IRRADIATION
PULSES
SURFACES
THERMOELASTICITY