Determination of plasma ignition threshold fluence during femtosecond single-shot laser ablation on metallic samples detected by optical emission spectroscopy

• Published in: Journal of analytical atomic spectrometry Vol. 3; no. 8; pp. 173 - 1735
• Main Authors: López-Claros, Marina, Vadillo, José M, Laserna, J. Javier
• Format: Journal Article
• Language: English
• Published: 01.01.2015
• Subjects: Ablation; Craters; Femtosecond; Fluence; Ignition; Laser ablation; Lasers; Thresholds
• ISSN: 0267-9477; 1364-5544
• DOI: 10.1039/c5ja00076a

The minimum laser fluence needed for plasma ignition on a sample during single-shot femtosecond laser ablation has been determined for a set of metals and alloys. Threshold fluence values ranged between 4 and 9 J cm −2 for ablation craters with a diameter of 40 μm. The craters exhibited similar size and shape regardless of the sample type, energy range (for energies per pulse <400 μJ) and accumulated energy dosage (<500 laser shots on the same sample position). The results obtained for the metals (Pb, Ag, Zn, Sn, Cr, Cu, W, Ni and Fe) show a clear trend of the fluence threshold with the work function, evidencing the importance of the surface electron excitation in femtosecond laser-matter interactions. Experiments with the alloyed samples reveal that fluence thresholds for femtosecond plasma ignition are matrix independent. The minimum laser fluence needed for plasma ignition on a sample during single-shot femtosecond laser ablation has been determined for a set of metals and alloys.