In der Arbeit wurden Abtragsverfahren zur Formgebung optischer Komponenten aus mineralischem Glas mittels ultrakurz gepulster Laserstrahlung analysiert. Aus den Untersuchungen zu ausgewählten Gläsern ergab sich, dass mit Verwendung ultrakurzer Laserpulse prinzipiell das gesamte Materialspek¬trum bearbeitbar ist. Für einen schichtweisen Abtrag wurden plausible Parameterräume definiert, in denen der Ablationsprozess stabil in Bezug auf die Zielgrößen (Rauheit, induzierte optische Gangunterschiede, Abtragstiefe, Schädigungstiefe sowie Abtragsraten) beschrieben werden kann. Es konnte festgestellt werden, dass sich in Relation zu einem spezifischen Vorbearbeitungszustand mit zunehmendem Abtrag und mithilfe einer gezielten Partikelabfuhr sowohl ein Gleichgewicht der Rauheit (eine Sättigungsrauheit) als auch linear fortschreitender Abtrag einstellt. Für dieses Abtragsverhalten an Glas wurden ein Modell für den 2,5D-Formabtrag aufgestellt, Aussagen zum Konditionierabtrag getroffen und Demonstratoren gefertigt.
In the scope of the present work, ablation processes for the shaping of optical components made of mineral glass using ultrashort pulsed laser radiation were investigated. For these investigations, an experimental ps and fs setup was designed, implemented, optimized and characterized, as well as analytical methods for sample evaluation. From the investigations on the selected glasses results the fact that with the use of ultrashort laser pulses, in principle, the entire material spectrum can be processed, although the processing results differ.
For a layered ablation, plausible parameter spaces have been defined, in which the ablation process can be described stably with respect to selected target values. Experimentally, the glass-specific bandgap and the applied wavelength showed increasing thresholds for the fluence necessary for ablation. When comparing pulse duration regimes, it was found that higher fluence values for ps-radiation must be applied for an onset of ablative ablation than for an ablation with fs-radiation. The investigations have shown that, in relation to a specific initial surface state of quartz glass, with increasing ablation, ie several crossings, and with the assistance of a modified removal of ablation particles a balance of roughness on the surface occurs and one could speak of a saturation roughness or preconditioned surface state. For this removal behavior of glasses, a model for the 2.5D shape removal with selected parameters was established and statements were made on the necessary conditioning removal. At the same time, after reaching the saturation value, a constant ablation regime resulted, which allowed a linear ablation per crossing. For a selection of processing parameters aimed at the target values (roughness, induced optical path differences, removal depth and removal rates), depths of subsurface damage have been determined. It turned out that the determined values are partly less than typical subsurface damage caused by fine and ultra-fine grinding (< 15 μm). These values help to shorten subsequent polishing processes. Layer by layer ablation with ultrashort pulses can be considered as substitution technology for the grinding process. In the applied laser parameter field, the determined material removal rates were < 14 mm³/min, well above the values of fine and ultra-fine grinding with ≈ 2 mm³/min.
In further investigations on the laser ablation with scan profiles, functional relationships could be described and demonstrated, which allow a spatially variable glass removal.