Enhanced efficiency and pulse-adjacency effects in high-repetition-rate laser machining

We observed enhanced efficiency in the machining of copper using a high-repetition-rate (10 kHz) Q-switched Nd :YLF laser. A significant increase of machining efficiency (material removed per unit time) was observed when the speed of lateral translation of the thin copper sheet across the beam focus was decreased. We attribute this increased efficiency to effects caused by pulse adjacency (i.e. partial overlapping) of several pulses at a given point on the target surface. Several mechanisms which might be responsible for the effect are discussed. Similar results were observed in experiments on laser trepanning. The observed increases in ablation rates might lead to improvements in some industrial processes, e.g. laser drilling, cutting and marking.