Laser-stimulated reactive atmospheric pressure plasma jet etching processes for ultra-precision processing of optical glasses (LasPlasJet)

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Ultra-precision shape generation and correction of optical surfaces such as lenses or mirrors by means of locally acting fluorine-containing atmospheric pressure plasma jets is based on a dry etching process and involves chemical reactions between the reactive species (fluorine radicals) formed in the plasma and the atoms of the substrate surface forming volatile products for simple silicon compounds, e.g. Si, SiO2, SiC. However, optical glasses considered in the project additionally contain metal oxides, which also form non-volatile reaction products during plasma jet etching, so that a uniform, temporally constant and roughness maintaining material removal cannot be achieved. Therefore, the research project aims at the experimental investigation of the physical and chemical interaction processes during the combination of pulsed reactive atmospheric pressure plasma jets and laser radiation in an etching process. The fundamental challenge of the topic is the determined influence on plasma jet based etching processes of composite, silicon based glasses by the application of a further, independently adjustable radiation energy, i.e. laser, which acts simultaneously or sequentially before or after the plasma jet etching. When plasma jet and laser radiation are combined, the additional initiation of chemical-physical processes in plasma jet etching can influence the material composition or structure in the near-surface area, so that an influence on the selectivity, homogeneity and the temporal and spatial constancy of the etch removal is expected. The main objective of the project is to gain a deeper scientific understanding of the mechanisms and processes involved in the combination of plasma jet and laser irradiation during the etching of complex glass materials. In the following, the gained knowledge will be used as a basis for the planned development of plasma jet / laser ultra-precision processing methods of glasses for high-end optical applications.