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

• Applicants: Professor Dr. Alexander Horn; Professor Dr. Steffen Weißmantel
• Subject Area: Joining and Separation Technology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 458053570

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.

• DFG Programme: Research Grants