Improving the efficiency of picosecond laser micromachining of stainless steel

Stainless steel was ablated by a 10 ps Q-switched Nd:VAN pulsed laser (Austria) in air under different operating conditions to explore high-efficiency ultrafast laser micromachining. The relationship between the ablation characteristics and laser parameters (number of pulses, fluence, wavelength and repetition rate) was analyzed through scanning electron microscopy and laser scanning confocal microscopy. The saturation pulses are approximately 2000-2500 in our experiments at varying other parameters attribute to the multi-pulse damage threshold of material. A critical fluence is found corresponding to the deepest hole and the optimized ablation efficiency which is related to the formation of dense plasma at the surface of the material. The short wavelength has significant advantages for the holes processing with high aspect ratios because of the lower optical absorption coefficient and the ablation threshold. Moreover, the maximum ablation depth with the least time could be achieved at the critical repetition rate owing to heat accumulation. These findings are expected to provide guidance to improve the efficiency of ultrafast laser micromachining.