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Study on the influence of repetition rate and pulse duration on ablation efficiency using a new generation of high power ytterbium doped fiber ultrafast laser

Ultrafast laser are well known to provide cold ablation on metals at near-threshold fluence and low repetition rate. However increasing the repetition rate from multi-kHz to MHz may produce a heat accumulation in the target depending on both the scanning speed and the material properties. This potentially leads to two effects: enhanced ablation efficiency as well as increased heat affected zone. To identify potentials and limitations while maintaining highest processing quality is the main objective of this paper and a key issue for many industrial applications. We present some comprehensive results on the influence of both repetition rate and pulse duration on the ablation efficiency. This investigation is performed using a new generation of high power Ytterbium doped fiber ultrafast laser with a tunable pulse duration ranging from 350fs to 10ps and with repetition rate going from 250kHz to 2MHz. The output power is up to 40 watt. The effect of both parameters above on ablation efficiency of Al, Cu and Mo is discussed with respect to removal rate measurement and SEM analysis.