DIRECT IN-SITU MEASUREMENT OF THE ABLATION RATE IN SHORT PULSE LASER PERCUSSION DRILLING OF METAL TARGETS

摘要

We demonstrate that a non-invasive sensingrntechnique based on optical feedback interferometry isrncapable to instantaneously measure the ablation frontrndisplacement and the removal rate during ultrafastrnlaser percussion drilling of metallic plates. Thernsawtooth-like modulation of the interferometricrnsignal out of the detecting sensor has been analyzedrnto reveal the time dependence of the removal depthrnwith sub-micrometric resolution. Various dynamicrnfactors related to the influence of laser pulse durationrnand peak energy have been assessed by in-siturnspatial- and time-dependent characterization allrnthrough the ablation process. The importance of realtimernmeasurement of the ablation rate is crucial tornimprove the basic understanding of ultrafast lasermaterialrninteractions. Moreover, the detection systemrnresults high-sensitive, compact, and easily integrablernin most industrial workstations, enabling therndevelopment of on-line control to improve thernablation efficiency and the quality of laser micromachiningrnprocesses.