A novel method is presented for determining the volume of molten material ejected from a substrate as a result of visible pulsed-laser ablation. A 100-μm-wide pulsed-laser light sheet (τ ~ 5 ns, λ = 532 nm) was used in conjunction with a CCD camera to provide high-speed cross-sectional images of single-pulse ablation of aluminum with a visible nanosecond laser source. Computational analysis of the two-dimensional gray-scale images was used to determine the total volume of material ejected from the substrate in the form of molten droplets. Ablation with dual-wavelength (511- and 578-nm) pulses of 30-ns duration was characterized under various fluence conditions (0–25 J cm<sup>−2</sup>), allowing a quantitative threshold for explosive melt ejection in aluminum to be established at ~10 J cm<sup>−2</sup>. The temporal evolution of the ejected material showed that, for an incident fluence of ~40 J cm<sup>−2</sup>, molten-droplet ejection commenced at ~400 ns and ceased after ~2 μs.
© 2004 Optical Society of America
Jennifer M. Fishburn, Michael J. Withford, David W. Coutts, and James A. Piper, "Method for Determination of the Volume of Material Ejected as Molten Droplets During Visible Nanosecond Ablation," Appl. Opt. 43, 6473-6476 (2004)