Acoustic Detection of Submicron Depth of Ablation Crater Formed on the Metal Surface under Nanosecond Laser Irradiation

Abstract

The recently published experimental data on the acoustic monitoring of the impact of a train of picosecond laser pulses with a total duration of about 500 ns and energy density up to 2 J cm⁻² on a metal have been analyzed. During monitoring, the behavior of the acoustic signal delay τ_n with respect to the laser signal has been recorded. A comparison of the average acoustic delay τ₀ for successive laser trains directed to the same target point (with a train-to-train interval of 30 s) shows a small variation in τ₀ (< 0.1 ns), which is indicative of weak effect of ablation on the behavior of τ_n during a laser train. Under the conditions of additional laser irradiation in the intervals between trains, acoustic delay measurements demonstrate an increase in the average delay τ0 for subsequent trains, which may be related to the metal surface ablation caused by the additional irradiation.