Laser processing of polycrystalline porous graphite through micro- to millisecond pulses with 1 µm wavelength is investigated. The study aims at finding the best compromise between the efficiency of the process (ablation rate) and the quality (reduced heat-affected zone) for drilling and cutting applications. Our experimental approach is based on experiments involving a monomode kW ytterbium fibre laser (1080 nm) coupled with a laser scanning system. This system is used for parametric studies on pulse duration, power, repetition rate and scanning speed on samples that are analysed with scanning electron microscopy. To improve the understanding of the underlying physical phenomena and processes involved, a finite element numerical model is developed, taking into account energy deposition through optical ray tracing, heat transfer, sublimation of the material and crater formation. Based on these experimental and numerical tools, we identify some optimum parameters to fabricate high aspect ratio shapes in graphite samples of 1.5 mm thickness with excellent edge quality and minimal heat-affected zone. Laser processing under vacuum atmosphere is also studied and exhibit no difference in behaviour compared to ambient atmosphere.

研究了通过 1 µm 波长的微至毫秒脉冲激光加工多晶多孔石墨。该研究旨在为钻孔和切割应用找到工艺效率（烧蚀率）和质量（减少热影响区）之间的最佳折衷。我们的实验方法基于涉及与激光扫描系统耦合的单模 kW 镱光纤激光器 (1080 nm) 的实验。该系统用于对用扫描电子显微镜分析的样品进行脉冲持续时间、功率、重复率和扫描速度的参数研究。为了更好地理解所涉及的潜在物理现象和过程，开发了一个有限元数值模型，考虑到通过光线追踪、传热、物质的升华和陨石坑的形成。基于这些实验和数值工具，我们确定了一些最佳参数，以在 1.5 毫米厚的石墨样品中制造高纵横比形状，具有出色的边缘质量和最小的热影响区。还研究了真空气氛下的激光加工，与环境气氛相比，其行为没有差异。