Investigation of UV-Femtosecond laser ablation on metallic substrates

Abstract Pulsed laser ablation is a common method for the analysis of material composition in solid materials. The use of femtosecond lasers allows for high depth resolution due to the low heat transfer into the material in metallic substrates. For such investigations, a sound knowledge of the ablation characteristics of the material is necessary. In this study, we present ablation thresholds and rates in a vacuum environment for tungsten, EUROFER 97, aluminum, copper, and bismuth using a laser setup capable of producing 400 fs, 343 nm pulses with a maximum intensity of 5 10^15\; W\, cm^-2. We find ablation thresholds of 530 mJ\, cm^-2, 200 mJ\, cm^-2, 370 mJ\, cm^-2, 360 mJ\, cm^-2 and 140 mJ\, cm^-2 for the materials, respectively. We also find minimum ablation rates of about 10 nm in all materials, showing the possibility of ablation experiments with a depth resolution of this order. The experiments on bismuth show an unexpected ablation behavior, since the ablation leads to strongly molten crater surfaces. An influence of the ratio of optical and thermal penetration depth on the ablation characteristics can be determined. The ablation data obtained in this study allow material characterization with high depth resolution femtosecond laser experiments.