Real-time in-situ measurement of the penetration depth in short pulse laser percussion drilling of metal targets

High-energy ultra-short pulse laser ablation is a fast-growing technology in precision laser micromachining of transparent as well as opaque materials. Accurate in-situ measurements of physical parameters such as the penetration depth and the removal rate are crucial to fully characterize the ultrafast laser-material interactions [1-5]. Nonetheless, the laser drilling is still lacking of a real-time technique able to monitor and control the spatial- and time-dependent evolution of the hole-depth in metallic plates.