Le Hoang, Penchev Pavel, Henrottin Anne, Bruneel David, Nasrollahi Vahid, Ramos-de-Campos Jose A, Dimov Stefan
Department of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK.
LASEA, Rue des Chasseurs Ardennais 10, 4031 Angleur, Belgium.
Micromachines (Basel). 2020 Feb 20;11(2):221. doi: 10.3390/mi11020221.
The uniform energy distribution of top-hat laser beams is a very attractive property that can offer some advantages compared to Gaussian beams. Especially, the desired intensity distribution can be achieved at the laser spot through energy redistribution across the beam spatial profile and, thus, to minimize and even eliminate some inherent shortcomings in laser micro-processing. This paper reports an empirical study that investigates the effects of top-hat beam processing in micro-structuring and compares the results with those obtainable with a conventional Gaussian beam. In particular, a refractive field mapping beam shaper was used to obtain a top-hat profile and the effects of different scanning strategies, pulse energy settings, and accumulated fluence, i.e., hatch and pulse distances, were investigated. In general, the top-hat laser processing led to improvements in surface and structuring quality. Especially, the taper angle was reduced while the surface roughness and edge definition were also improved compared to structures produced with Gaussian beams. A further decrease of the taper angle was achieved by combining hatching with some outlining beam passes. The scanning strategies with only outlining beam passes led to very high ablation rates but in expense of structuring quality. Improvements in surface roughness were obtained with a wide range of pulse energies and pulse and hatch distances when top-hat laser processing was used.
平顶激光束的均匀能量分布是一种非常吸引人的特性，与高斯光束相比具有一些优势。特别是，通过在光束空间分布上重新分配能量，可以在激光光斑处实现所需的强度分布，从而最小化甚至消除激光微加工中的一些固有缺点。本文报道了一项实证研究，该研究调查了平顶光束加工在微结构化中的效果，并将结果与传统高斯光束加工的结果进行了比较。具体而言，使用了一种折射场映射光束整形器来获得平顶分布，并研究了不同扫描策略、脉冲能量设置以及累积能量密度（即扫描间距和脉冲间距）的影响。总体而言，平顶激光加工提高了表面质量和结构化质量。特别是，与高斯光束加工产生的结构相比，锥角减小，表面粗糙度和边缘清晰度也得到了改善。通过将扫描与一些轮廓光束扫描相结合，进一步减小了锥角。仅采用轮廓光束扫描的策略导致了非常高的烧蚀速率，但牺牲了结构化质量。当使用平顶激光加工时，在广泛的脉冲能量、脉冲和扫描间距范围内，表面粗糙度都得到了改善。
