Ultrasound generated by a femtosecond and a picosecond laser pulse near the ablation threshold
- 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, Vol. 98, Issue 3; Other Information: DOI: 10.1063/1.1999827; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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