High roundness and cross-scale capillary fabrication on sapphire by femtosecond laser ablation

We introduce a laser processing strategy for fabricating capillaries with gradually varying diameters and curvature on sapphire. By dividing the capillaries into the variable power region and the fixed power region, we have reduced the impact of energy loss caused by debris accumulation during the machining process, leading to improved roundness. We investigate the creation of morphological deviations caused by motion errors. Utilizing the varying impacts of scanning paths in reducing motion errors, we propose rules for developing laser scanning paths for different capillary structures. We have successfully fabricated capillaries with diameters ranging from 50 mu m to 800 mu m and lengths extending to centimeter-scale dimensions. The roughness measurement is below 100 nm, and roundness errors are less than 5 mu m. These capillaries with diverse configurations, including gradually varying diameters and curvature, are successfully applied to laser wakefield acceleration experiments and accelerate electrons along the curved capillary to GeV level.