Effect of surface roughness on the ultrashort pulsed laser ablation fluence threshold of zinc and steel

• Published in: Applied surface science 2019-09, Vol.488, p.10-21
• Main Authors: Mustafa, H., Mezera, M., Matthews, D.T.A., Römer, G.R.B.E.
• Format: Article
• Language: English
• Subjects: Ablation threshold; Galvanized steel; Polycrystalline zinc; Surface roughness; Titanium stabilized ultra-low carbon steel; Ultrashort pulsed laser
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.05.066

The single and multiple pulse laser ablation threshold of zinc and steel at picosecond laser pulse duration is studied as a function of initial surface roughness at laser wavelengths of 515 and 1030 nm. The initial surface topographies and the resulting crater morphologies are analyzed using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Reflectivity measurements of the initial surfaces show increased absorptivity with increasing surface roughness. It was found that the single pulse ablation threshold increases with increasing effective surface area; the latter resulting from surface roughness. Rougher surfaces tend to have a higher degree of incubation as well. From the experimental and simulation results, it appears that the absorbed energy contributes more to residual heat than to material ablation when effective surface area increases. [Display omitted] •Increase in surface roughness increases the effective surface area exposed to laser irradiation.•Absorptivity of the materials and ablation fluence threshold increases with increasing effective surface area.•Due to local topological differences, the temperature distribution is non-uniform.•Therefore, most of the absorbed energy ends up as residual heat rather than contributing to material ablation.