Surface roughness plays a critical role in ultrashort pulse laser ablation,
particularly for industrial applications using burst mode operations,
multi-pulse laser processing, and the generation of laser-induced periodic
surface structures. Hence, we address the impact of surface roughness on the
resulting laser ablation topography predicted by a simulation model and
compared to experimental results. We present a comprehensive multi-scale
simulation framework that first employs finite-difference-time-domain
simulations for calculating the surface fluence distribution on a rough surface
measured by an atomic-force-microscope followed by the two-temperature model
coupled with hydrodynamic/solid mechanics simulation for the initial material
heating. Lastly, a computational fluid dynamics model for material relaxation
and fluid flow is developed and employed. Final state results of aluminum and
AISI 304 stainless steel simulations demonstrated alignment with established
ablation models and crater dimension prediction. Notably, Al exhibited
significant optical scattering effects due to initial surface roughness of 15
nm – being 70 times below the laser wavelength, leading to localized, selective
ablation processes and substantially altered crater topography compared to
idealized conditions. Contrary, AISI 304 with RMS roughness of 2 nm showed no
difference. Hence, we highlight the necessity of incorporating realistic,
material-specific surface roughness values into large-scale ablation
simulations. Furthermore, the induced local fluence variations demonstrated the
inadequacy of neglecting lateral heat transport effects in this context.

Dieser Artikel untersucht Zeitreisen und deren Auswirkungen.

PDF herunterladen: