Residual stress in Germanium single crystals caused by femtosecond laser micromachining

Femtosecond laser (fs-laser) milling has emerged as a promising technique for high-precision material processing, offering significantly faster ablation rates compared to Ga+ Focused Ion Beam (FIB) milling. While fs-laser ablation is often considered to be athermal, its impact on surface features, such as redeposited material, raises concerns about its influence on microstructure and residual stress fields. This study explores the mechanical effects of fs-laser and FIB milling on a germanium single crystal, using synchrotron-based Laue microdiffraction coupled with Digital Image Correlation to characterize induced residual stresses and their spatial distribution. The further development of this technique allows to push the strain resolution to 10⁻⁵, which enabled a clear identification of the influence of the redeposition structure.