Abstract: The influences of polarization state on ablation line width and morphology are investigated based on line experiments of different laser power. The surface ablation experiments of different line overlap rate δ are carried out in the combination of linear ablation optimized parameters. Also, the surface roughness is analyzed by using surface profiler. In addition, the relational expressions of scanning velocity and line overlap rate on the influence of scallop height are established, and then the expressions are calculated. The results show that the ablation line quality of linearly polarized laser is better than the circularly polarized laser, and its line width is greater than that of circularly polarized laser. When δ increases from 65% to 90%, the arithmetical mean deviation Ra of ablation surface for linearly polarized laser decreases firstly and then increases, and it reaches to a minimum of 1.05 μm at δ=80%. But, the Ra of circularly polarized laser decreases with the increasing of δ, and it reaches to a minimum of 1.63 μm at δ=90%. The calculated results of roughness Rz are consistent with the experimental results, and it is a kind of linear relation between Rz and δ. Also, the Rz decreases with the increasing of δ.

Key words: ablation morphology, femtosecond laser, line overlap rate, polarization state, surface roughness