Coupling effect of evaporation-plasma shielding and its influence on femtosecond laser ablation

The two-temperature model is employed to investigate the evaporation and plasma shielding coupling effect by femtosecond ablation during the ablation of gold films. The plasma shielding effect is characterized by coupling the plasma expansion dynamics with the electron source term. The evaporation effect is realized by the liquid–vapor interface tracking method. The simulation results show that the reflectivity and absorption coefficient decrease from 0.488 and 486 μm⁻¹ to 0.293 and 180 μm⁻¹, respectively, due to the electron heating by the femtosecond laser with 120 fs pulse width and 5000 J/m² energy density. The electron and phonon temperatures increase sharply because the gold film absorbs more energy. While the heating interval is 10 ps, the plasma absorbs 30% laser energy. Moreover, the plasma shielding effect is enhanced with the increasing laser energy density in the 2500–15000 J/m² range. The influence of plasma on laser-irradiated gold film can be weakened by controlling the pulse interval time. It is helpful to improve the accuracy and efficiency of femtosecond laser processing.