Fabrication of Rectangular Micro-Channels by Ultrashort Pulse Ablation Using a Bessel Beam

This paper reports on combining non-diffracting Bessel beams and ultra-short pulsed laser ablation for the generation of micro-channels.The small focal spot and the long focus depth make Bessel beams suitable as an ideal tool for fabricating sharp-edged channels.In this context, we present a study on the generation of rectangular micro-channels that are highly interesting for future investigations on material properties of additive manufactured and cast aluminum samples, e.g., using them as initial notches or defects, respectively, for fatigue and damage tolerance assessment.In order to achieve the highest quality of rectangular microchannels, optimal processing conditions were achieved by analyzing the influence of the laser power, the number of exposure cycles, and the axial position of the sample on the ablation process.Similar experiments using a Gaussian Beam were performed to compare the different beam shapes regarding the resulting channel geometry and ablation efficiency.Nevertheless, the walls of the Bessel beam processed channels are almost perpendicular to the surface and the bottom of the channel is almost flat.Thus, the Bessel beam generated micro-channels are more rectangular than the ones processed with the Gaussian beam.