Microscopic and macroscopic simulations for femtosecond-laser-matter interaction by cubic interpolated propagation...

We performed 1.5-dimensional simulation for the Fokker-Planck equation using the CIP (cubic-interpolated propagation/constrained interpolation profile) method to investigate femtosecond-laser heating and transport processes. We found that the heat flux in the solid part approaches the Spitzer-Härm theory on quite a short time scale omega(p)t<50, and thus the subsequent evaporation process can be analyzed by classical thermal conduction. On the basis of this result, we performed a hydrodynamic simulation using the CIP method with classical thermal conduction in order to investigate the long time behavior of the evaporation process. The experimental ablation depth was replicated very well, showing that even femtosecond pulse laser processing can be satisfactorily described by classical heat conduction. Since the damage size is shown to be much larger than laser-spot size even in such an ultrashort-pulse experiment, we must use the fluence estimated by the damage size, which is twice as large as the laser spot, to correctly replicate the experiments.