The Effect of Laser Pulse Duration and Feed Rate on Pulsed Laser Polishing of Microfabricated Nickel Samples

The objective of this work was to improve our understanding of pulsed laser micropolishing $(PLμP)$ by studying the effects of laser pulse length and feed rate (pulses per millimeter) on surface roughness. $PLμP$ experiments were conducted with a multimode neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (1064 nm wavelength) that was focused down to approximately $50μm$ diameter and scanned over the stationary workpiece surface. Simulation results presented here and previous work suggest that longer laser pulses result in smoother surfaces. Results on microfabricated nickel samples using laser pulse durations of 300 ns and 650 ns test this hypothesis. Polishing with 300 ns and 650 ns pulse durations results in an average surface roughness of 66 nm and 47 nm, respectively; reductions of 30% and 50% compared with the original surface. Furthermore, $PLμP$ is shown to introduce a minor artifact on the sample surface whose spatial frequency (1/mm) is directly related to the laser feed rate (pulses/mm).