Interaction of bursts of ultrafast laser radiation in the GHz to MHz regime with metals - MULTIPULSE

研究了金属与重复频率在千兆赫兹至兆赫范围内的超快激光辐射的相互作用，以定量地解释烧蚀结构的拓扑结构的变化和由此产生的每个脉冲的波动烧蚀体积作为脉冲数和它们的时间距离的函数。此外，对超快激光辐射与材料相互作用的理解使得能够确定最佳参数，以便在后续项目中使用超快激光辐射的突发有效生成高质量结构。因此，所有发生的效应，例如由于热积聚而改变的材料表面，材料表面上的烧蚀云的材料的孵化和再沉积以及相互作用，通过烧蚀结构的非原位分析来补充地研究后续脉冲的激光辐射与现有等离子体或烧蚀云的相互作用（反射、透射和吸收），材料的光学响应的原位测定，以及激光辐射与材料的相互作用的建模。因此，计划中的项目分为三个工作包，即AP 1准备、AP 2双脉冲和AP 3多脉冲，每个工作包的复杂性和知识都在不断增加。调查包括工艺和材料参数的变化（材料：在玻璃衬底上沉积为具有不同层厚度的层的金和铁;激光辐射的参数：注量、脉冲持续时间、脉冲数、时间脉冲距离）、时间和空间分辨计量学的使用（泵浦-探测反射测量法、椭圆偏振测量法和阴影摄影法）以及激光辐射与材料的相互作用的建模（双温度模型结合流体力学TTMHD、相图、激光辐射通过烧蚀云的传播）。由此，确定所施加的超快激光辐射的突发的参数与所生成的烧蚀结构之间的关系和依赖性。

The interaction of metals with bursts of ultrafast laser radiation with repetition rates in the gigahertz to megahertz range is investigated to quantitatively explain the change of the topology of the ablation structure and the resulting fluctuating ablation volume per pulse as a function of the number of pulses and their temporal distance. Additionally, the understanding of the interaction of the ultrafast laser radiation with the material enables the determination of optimal parameters for the efficient generation of high-quality structures using bursts of ultrafast laser radiation in follow-up projects. Therefore, all occurring effects, such as the altered material surface due to heat accumulation, incubation and re-deposition of material from the ablation cloud on the material surface as well as the interaction (reflection, transmission, and absorption) of the laser radiation of a subsequent pulse with an existing plasma or ablations cloud are complementarily investigated by an ex-situ analysis of the ablation structure, an in-situ determination of the optical response of the material, and the modeling of the interaction of the laser radiation with the material. The planned project is therefore divided into three work packages, AP1 preparation, AP2 double pulse, and AP3 multi-pulse, each with increasing complexity and progressive knowledge. The investigations include a variation of the process and material parameters (material: gold and iron deposited as layers with different layer thicknesses on a glass substrate; parameters of the laser radiation: fluence, pulse duration, number of pulses, temporal pulse distance), the use of time- and space-resolved metrology (pump-probe reflectometry, - ellipsometry and - shadow photography), and the modeling of the interaction of the laser radiation with the material (two-temperature-model in combination with hydrodynamics TTMHD, phase diagrams, propagation of the laser radiation through the ablation cloud). Thereby, the relationships and dependencies between the parameters of the applied bursts of ultrafast laser radiation with the generated ablation structures are determined.