Abstract
In this paper, the influence of the pulse duration on the ablation threshold and the incubation coefficient was investigated for three different types of materials: metal (copper), semiconductor (silicon) and biopolymer (gelatin). Ablation threshold values and the incubation coefficients have been measured for multiple Ti:sapphire laser pulses (3 to 1000 pulses) and for four different pulse durations (10, 30, 250 and 550 fs). The ablation threshold fluence was determined by extrapolation of curves from squared crater diameter versus fluence plots. For copper and silicon, the experiments were conducted in vacuum and for gelatin in air. For all materials, the ablation threshold fluence increases with the pulse duration. For copper, the threshold increases as τ 0.05, for silicon as τ 0.12 and for gelatin as τ 0.22. By extrapolating the curves of the threshold fluence versus number of pulses, the single-shot threshold fluence was determined for each sample. For 30 fs pulses, the single-shot threshold fluences were found to be 0.79, 0.35, and 0.99 J/cm2 and the incubation coefficients were found to be 0.75, 0.83 and 0.68 for copper, silicon and gelatin, respectively.
Highlights
Ultrafast lasers have been of increasing interest in material processing applications due to their capability of precise micromachining of a large variety of materials: metals, semiconductors, polymers, dielectrics, biological materials, etc [1]
In this paper, the influence of the pulse duration on the ablation threshold and the incubation coefficient was investigated for three different types of materials: metal, semiconductor and biopolymer
Ablation threshold values and the incubation coefficients have been measured for multiple Ti:sapphire laser pulses (3 to 1000 pulses) and for four different pulse durations (10, 30, 250 and 550 fs)
Summary
Ultrafast lasers have been of increasing interest in material processing applications due to their capability of precise micromachining of a large variety of materials: metals, semiconductors, polymers, dielectrics, biological materials, etc [1]. The actual physical mechanisms of laser ablation depend on the type of materials and the irradiation properties such as laser wavelength [10], pulse duration [13,14,15,16,17,18,19] and repetition rate [14, 20]. It leads to heat accumulation that causes melting The latter, especially in case of metals with a relatively low thermal conductivity, prevents the high level of precision which is achievable at lower repetition rates. Many authors have investigated the dependence of ablation threshold fluence on various laser parameters, but most studies were limited to a particular pulse duration or number of shots or material. The dependence of the threshold fluence on the pulse duration was determined as Fth μ s0.05 for copper, Fth μ s0.12 for silicon and Fth μ s0.22 for gelatin
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