Ultrafast Laser Machining of Micro Grooves in Metals with Spatially Optimized Intensity Distribution

Abstract : Femtosecond laser processing of metals knows a particular interes due to the possibility to machine many materials with a high degrtee of precision and reduced side effects around the interaction zone. For example, recent developments have taken advantage on the possibility to temporally tailor the light pulse sequence in order to enhance the ablation efficiency on steel. On the spatial aspect, beam multiplexing have become an efficient and well-mastered technique to reduce the processing time and cost by multiplying the number of processing foci on the sample. This report concerns the influence of the spatial intensity distribution during surface processing of grooves in metals in a dynamic irradiation scheme (i.e. when the focal spot is displaced with respect to the surface of the sample). More precisely, we underline the effect of intensity gradient in the beam profile and show that the gradient direction with respect to the sample translation direction can play a paramount role in the quality of the achieved micro-groove. We also show that this technique can be combined with multispot processing.