CO2 laser processing of fused silica: a review of mechanisms, defect control and functionalization

Fused silica optics are critical components in inertial confinement fusion facilities, where they are exposed to intense ultraviolet laser radiation. However, processing induced subsurface defects serve as laser damage precursors, severely degrading the laser-induced damage threshold (LIDT) and constraining the output energy of high-power laser systems. CO 2 laser processing has emerged as a pivotal technology for mitigating these defects and repairing laser-induced damage, owing to its non-contact operation, pollution-free nature, and high absorption efficiency in fused silica. Nevertheless, its transition from laboratory research to engineering application is hindered by challenges such as residual stress, raised rims, subsurface bubbles, and the decoupling of LIDT enhancement from geometric accuracy control. This review provides a comprehensive synthesis of CO 2 laser processing of fused silica, mapping the entire technological chain from fundamental mechanisms to advanced functionalization. The underlying physical principles are systematically examined, including transient thermal fields, structural relaxation and fictive temperature modeling, melt pool dynamics, evaporative ablation, and thermo-mechanical stress generation, alongside the predictive multi-scale models that quantify these interconnected processes. Building on this mechanistic foundation, the technological evolution from local-defect repair to full-aperture, low-defect manufacturing is critically analyzed. Key strategies for defect risk control are evaluated, and the paradigm shift from subtractive repair to functional manufacturing is delineated. Advances in CO 2 laser-based subtractive fabrication and additive manufacturing are reviewed, highlighting the integration of hybrid processes and unconventional synthesis routes. Finally, the outlook identifies priority directions: nanoscale precursor identification, multimodal real-time monitoring, and scalable large-area manufacturing strategies. By emphasizing mechanism-process linkages and engineering scalability, this review establishes a roadmap for overcoming performance bottlenecks and accelerating the deployment of laser-based advanced manufacturing for high-damage-resistant, functionally integrated fused silica optics.