Picosecond-pulsed laser ablation of aluminum foils: crater morphology and plasma parameters

In this study, the ablation process that occurs on the surface of aluminum foil (Al) using picosecond-duration Nd: YAG laser pulses (λ = 1064~nm,\ τ = 28~ps) and the physical properties of the resulting laser-induced plasma are comprehensively investigated. In the performed experiments, we used laser fluences ranging from 16.37 to 21.17 J/cm². The shape and dimensions of the craters formed on the surface are precisely analyzed using a Scanning Electron Microscope (SEM). Additionally, the spectral emission of the plasma is also examined using optical emission spectroscopy. The experimental results revealed a strong linear correlation between the diameter of the crater and the plasma electron density (R = 0.96). Our finding suggests the potential of laser-induced breakdown spectroscopy (LIBS) technology for improved precision and the development the minimally destructive surface analysis approaches. The plasma temperature is determined on the basis of the Boltzmann distribution and found to have a direct dependence on the laser fluence. An increase in laser intensity resulted in a corresponding increase in the hydrodynamic length of the plasma. Furthermore, the inverse Bremsstrahlung absorption coefficient, which takes an account the energy absorption in the plasma, is calculated, and its dependence on the laser fluence is confirmed with a high level of statistical confidence (R² = 0.99556).