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Mechanical polishing of glass is a time consuming process especially for lenses deviating from spherical surface such as aspheres. With laser polishing, the processing time can be significantly reduced and the wear of hard tooling can be avoided. Using laser radiation for polishing, a thin surface layer of the glass is heated up just below evaporation temperature due to the interaction of glass material and laser radiation. With increasing temperature, the reduced viscosity in the surface layer leads to the reduction of the roughness due to the surface tension. Hence, a contactless polishing method can be realized nearly without any loss of material or need of polishing agent. In this paper, results for laser polishing of fused silica, BK7, and S-TIH6 are presented with area rates up to 5 cm2/s. However, the results show that the achieved roughness with laser polishing is strongly influenced by the thermal properties of the type of glass. During laser polishing, the glass material is relocated at the surface, thus no shape errors can be corrected. To reduce the residual waviness and shape errors after laser polishing, the authors investigated a further laser-based process step (laser beam figuring, LBF) which ablates material for a shape correction. Ablation depths <5 nm allow a high precision laser ablation for selective processing. For both processes, a CO2 laser is used

This study presents the development of post-processing steps for microfluidics fabricated with selective laser etching (SLE) in fused silica. In a first step, the SLE surface-even inner walls of microfluidic channels—can be smoothed by laser polishing. In addition, two-photon polymerization (2PP) can be used to manufacture polymer microstructures and microcomponents inside the microfluidic channels. The reduction in the surface roughness by laser polishing is a remelting process. While heating the glass surface above softening temperature, laser radiation relocates material thanks to the surface tension. With laser polishing, the RMS roughness of SLE surfaces can be reduced from 12 µm down to 3 nm for spatial wavelength λ < 400 µm. Thanks to the laser polishing, fluidic processes as well as particles in microchannels can be observed with microscopy. A manufactured microfluidic demonstrates that SLE and laser polishing can be combined successfully. By developing two-photon polymerization (2PP) processing in microchannels we aim to enable new applications with sophisticated 3D structures inside the microchannel. With 2PP, lenses with a diameter of 50 µm are processed with a form accuracy rms of 70 nm. In addition, this study demonstrates that 3D structures can be fabricated inside the microchannels manufactured with SLE. Thanks to the combination of SLE, laser polishing and 2PP, research is pioneering new applications for microfluidics made of fused silica

Recent results of processing fused silica using a high-power Q-switched CO₂ laser source with a maximum output power of 200 W are presented. Compared to the processing with continuous wave laser radiation, the main advantage of pulsed laser radiation is the influence of the light-matter interaction with high laser peak power at small average laser power. An application for the approach presented in this paper is the flexible manufacturing and form correction of optics. This laser-based process is nearly independent of the surface geometry and can even be enhanced by laser polishing and expanded to other glass materials. Hence, the high-power Q-switched CO₂ laser source is used to ablate glass material with an ablation rate up to 2.35  mm³/s and also for ablating glass material locally in a vertical dimension down to 3 nm.

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