Pulse duration and energy density influence on laser processing of metals with short and ultrashort pulses

Abstract

Influence of pulse duration on microprocessing of Al is studied. Results show noticeable differences in terms of quality, burr height and remolten or recast matter into micromachined grooves at high fluence regime for 120fs and 4,5 ps pulse duration. At 120 fs experimental results of penetration depth are found to be 2 or 3 times higher than the theoretical optical penetration depth and is lowered to this value with increasing pulse duration. At high fluence regime up to 2 J/cm2, ablation thresholds are found to be in the range 10 times higher than for the case of 1 J/cm2. Penetration depths are higher by a factor 10 to 20 than the theoretical optical penetration depth. The ablation rate is nearly constant until 1 ps and then falls down to 2 times lower values and decreases regularly until 4,5 ps. This time is supposed to correspond to a critical pulse width between ultrashort and short regime.