Formation mechanism of ablation textures morphology involved in laser ablation of fused silica: A cross-dimensional study from single-point to line and area ablation

Laser processing is widely used in the field of optical material processing due to its high efficiency and high precision. However, the surface ablation textures formed by material removal under pulsed laser irradiation seriously degrade the surface quality. To reveal the formation mechanism of ablation textures, this work combines multi-physics simulation and experiments to investigate the evolution process of ablation textures during cross-dimensional ablation, and the morphological composition of the ablated surface at different spatial frequency band. The morphology and temperature evolution laws under multi-pulse single-point laser irradiation are explored, and the nonlinear evolution process of texture height and pit bottom position during variable-energy laser line ablation are obtained. Through parameter optimization, the texture height can be controlled within 40 nm. Subsequently, experiments are conducted to explore the morphological composition of the ablated surface at different spatial frequency bands. The laser-induced periodic surface structures (LIPSS) caused by photon polarization dominate the microscopic roughness. The periodic textures formed by scanning laser ablation and morphological superposition are the main contributor to the mesoscopic surface topography. Thermal deformation of the ablated surface induced by thermal accumulation is the primary factor for the formation of macroscopic surface morphology. Using optimized ablation parameters, the surface roughness Sa of fused silica material after ablation removal can be improved to better than 100 nm. This work can provide a theoretical basis for understanding the formation mechanism of ablated surface morphology, and offer parameter guidance to enhance the ablation surface quality.