Precise processing of optical glass by laser-induced reactive plasma etching at atmospheric pressure

• Applicants: Dr. Martin Ehrhardt; Dr.-Ing. Klaus Zimmer
• Subject Area: Coating and Surface Technology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 554597436

Ultrahigh-precision machining processes with beam tools such as ion beams or plasma jets are becoming increasingly important for optical and electronic applications. Many of these applications are not accessible for laser ablation processes, as the accuracy of this physically dominated process is not sufficient in terms of depth resolution, roughness, and material changes in the near-surface area. However, etching with laser-induced plasmas offers excellent conditions for ultrahigh-precision surface treatment processes, as machining rates of less than 10 pm per laser pulse, roughness in the range of 1 nm rms and damage depths in the range of 1 nm have been demonstrated. In this project, these characteristics of ultrahigh-precision surface processing are transferred to laser-induced plasma etching process for optical glasses, which can have a significantly more complex chemical composition. This complicated composition of the glasses can lead to changes in the mechanism of the etching process and possibly also in the achievable surface quality. Furthermore, the use of high-repetition ultrashort pulse lasers is also planned for the laser-assisted etching process, which on one hand should increase the etching/processing speed and on the other hand is expected to cause significant changes in the mechanisms of laser-induced plasma formation and its etching attack. These scientific findings will be used to demonstrate a laser-assisted ultrahigh-precision machining process for application-relevant glass surfaces with complex compositions, such as BK7 and Zerodur. The demonstration includes the etching of surfaces by moving the laser focus, the locale adjustment of the etching by controlling the laser spot speed and the application of the methodology to generate a functional surface in the aforementioned glasses.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Angelika Beyertt