Simulations of controlled spectral emission of Al plasmas generated by temporally tailored laser irradiation
Résumé
Hydrodynamics simulations and irradiation experiments were performed to correlate ultrashort intensity envelopes of the laser fields and thermodynamical states reached by the emerging plasma phase in ablation regimes. We discuss the efficiency of energy coupling as a function of different intensity envelopes and the resulting temperature, density and ionization states since the energy delivery rate is an essential factor that predetermines the material thermodynamic evolution. Subsequently, we examine the plasma composition in calculating the proportion of neutral/ion species typical of LIBS signals and comparing it with neutral/ion ratios given by experimental results. Moreover, the calculations allow to investigate the efficiency of nanoparticles generation from materials subjected to different heating rates. These can be related to hydrodynamic ejection of nanosized liquid layers upon the action of mechanic waves. With support from numerical simulations of the hydrodynamic advance of the excited matter, experiments revealed that mastering intensity envelopes of ultrashort laser pulse leads to further control on the ablation products. Emerging plasma phase in a hot state generates specific spectral emission patterns that can serve as indicators for its controlled formation and kinetic evolution.