Picosecond and Nanosecond Pulsed Laser Ablation of Aluminium Foil

The pulsed laser ablation of 20 micron thick aluminium foil is investigated by exposing moving samples to picosecond pulses of wavelength 1064nm and nanosecond pulses of wavelength 515nm and 1030nm. Ablation thresholds and depths are determined for a range of conditions using an optical microscope and 3D optical profiler. Complete three-dimensional crater profiles for single and multiple pulses are presented. The results reveal a variation in ablation threshold with wavelength, pulse duration and the number of pulses; a large reduction is observed for picosecond pulses. Ablation rates per pulse are expressed by general equations and found to vary strongly with both laser type and the number of pulses. The green nanosecond laser is found to ablate most efficiently for fluences above 10J/cm², whilst the picosecond source is instead advantageous for low fluences. A large reduction in ablation depth per pulse is observed with an increasing number of pulses. The present work affords prediction of scribe and cut parameters for the processing of thin aluminium layers and, more generally, characterises the driving parameters of pulsed picosecond and nanosecond laser ablation of metals.