2005
DOI: 10.1063/1.1999827
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Ultrasound generated by a femtosecond and a picosecond laser pulse near the ablation threshold

Abstract: We have investigated high-frequency ultrasound generated by single laser pulses in thin (50μm) aluminum foils as a function of the laser fluence. Laser-pulse durations of 80fs and 270ps 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-μm propagation through the foils for the two laser-pulse durations in the fluence range of 0.1–0.7J∕cm2. For fluences greater than th… Show more

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Cited by 18 publications
(7 citation statements)
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“…The observation of P max+ ≈ 7 bar for each 8 ns laser pulse over thousands of laser pulses confirms the generation intense US waves at laser fluences below the ablation threshold of polystyrene. The higher P max+ obtained with the 30 ps laser agrees with the expected dependence on the laser peak intensity 31 , and the reproducibility of the corresponding PA waves for at least 10 min at 10 Hz shows that the ablation threshold was not attained although the optical power density reached 3.33 GW/cm 2 , in accordance to other systems 32 .…”
Section: Discussionsupporting
confidence: 87%
“…The observation of P max+ ≈ 7 bar for each 8 ns laser pulse over thousands of laser pulses confirms the generation intense US waves at laser fluences below the ablation threshold of polystyrene. The higher P max+ obtained with the 30 ps laser agrees with the expected dependence on the laser peak intensity 31 , and the reproducibility of the corresponding PA waves for at least 10 min at 10 Hz shows that the ablation threshold was not attained although the optical power density reached 3.33 GW/cm 2 , in accordance to other systems 32 .…”
Section: Discussionsupporting
confidence: 87%
“…Generally, the ablation threshold is around 10 8 W cm −2 . 8,11,16,17 At this power density, the irradiated foil undergoes such an extreme temperature change that a metal plasma is formed. 18 A more detailed description of how this ablation occurs will be given below but, for now, the generation of acoustic waves is the focus.…”
Section: Generation Of Acoustic Waves For Laser-induced Acoustic Desomentioning
confidence: 99%
“…Ablation of the foil happens much faster than the laser pulse, which is on the nanosecond timescale. 17 Therefore, after the leading edge of the laser pulse causes ablation, the plume of metal ions that was ejected covers the path of the laser and absorbs part of the remaining laser pulse energy. 5,6 Using a laser power density with an optimal magnitude causes ablation after most of the laser pulse has reached the foil and, hence, provides higher amplitude acoustic waves.…”
Section: Experimental Parameters Influencing Laser-induced Acoustic Dmentioning
confidence: 99%
“…There has been a number of works devoted to laser pulsed generation of acoustic waves in thermoelastic and ablative regimes in metals. [4][5][6][7][8][9][10][11][12] However, limited attention has been paid to laser ultrasonic regime when the laser pulse energy is sufficient to melt solids but not enough to ablate them. Previously few researchers have investigated signal amplitude changes for shear acoustic waves in AISI 304 stainless steel 13 and for surface acoustic waves in silicon 14 under nanosecond laserinduced melting, with recent work on Si melting using time-resolved sub-nanosecond reflectometry.…”
Section: Introductionmentioning
confidence: 99%