Laser-based manufacturing of fused silica optics: figure error correction using laser beam figuring

Demand for complex, application-specific optics requires processes that deliver high surface quality and figure accuracy at reduced cost and lead time. This work investigates laser beam figuring (LBF) as a deterministic, laser-based step in an integrated manufacturing chain for fused silica optics. LBF uses spatially selective CO₂-laser irradiation to remove material in the nanometer range according to the difference between the actual and target surface geometry. Pulse-duration modulation enables precise depth control while maintaining low surface roughness. Building on previous studies, we address two critical gaps in the state-of-the-art. First, we experimentally determine the long-term stability of laser-induced densified regions over an unprecedented 80-week observation period, demonstrating statistically robust process stability essential for industrial applications. Second, we systematically map the transition from densification-dominated regimes (< 10 nm) to true ablation, identifying optimal process windows (dx = 10 μm, dy = 30 μm) that enable reproducible nanometer-scale figure correction with area rates competitive to conventional methods. Figure error correction experiments demonstrate RMS reduction from 79.2 nm to 30.6 nm in a single pass. However, LBF introduces high-frequency surface features (λ < 100 μm), suggesting integration with chemo-mechanical post-polishing for applications requiring ultra-smooth surfaces. The results provide a quantitative foundation for LBF as a complementary technology to ion beam figuring and magnetorheological finishing, particularly suited for rapid prototyping and laser-based process chains.