Laser-based defect characterization and removal process for manufacturing fused silica optic with high ultraviolet laser damage threshold

Ultraviolet (UV) laser-induced damage to fused silica optics has significantly limited development of high-energy laser systems.The fundamental reason is that the processing defects introduced by current contact grinding and polishing processes are difficult to remove completely, which greatly reduces the damage resistance of the optics.In this study, we demonstrate the manufacturing of fused silica optics with a high damage threshold using a CO2 laser process chain (including laser ablation, laser cleaning, and laser melt polishing).Based on theoretical and experimental studies, the proposed uniform layer-by-layer laser ablation technique can be used to characterize the subsurface mechanical damage in three-dimensional full aperture.Longitudinal ablation resolutions ranging from nanometers to micrometers can be realized; the minimum longitudinal resolution is < 5 nm.This technique can also be used as a crack-free grinding tool to completely remove subsurface mechanical damage, and as a cleaning tool to effectively clean surface/subsurface contamination.Through effective control of defects in the entire chain, the laser-induced damage thresholds of samples fabricated by the CO2 laser process chain were 41% (0% probability) and 65.7% (100% probability) higher than those of samples fabricated using the conventional process chain.This laser-based defect characterization and removal process provides a new tool to guide optimization of the conventional finishing process and represents a new direction for fabrication of highly damage-resistant fused silica optics for high-energy laser applications.