Temporal pulse shaping effects on aluminium and boron ablation plumes generated by ultrashort pulsed laser ablation and analyzed by time- and space-resolved optical spectroscopy

This paper focuses on the effect of temporal shaping of femtosecond laser pulses on laser ablation of aluminium and boron. The influence on plasma composition is deduced from optical emission investigations. Irradiation generated by the temporal tailoring of an incident laser pulse into double pulses or longer pulses is examined and compared to results deduced from hydrodynamic simulations of plasma temperature profiles. Above the ion formation threshold, increasing the delay in the double pulses sequence or increasing the pulse duration leads to an increase of the ion emission of the plasma plume of aluminium or boron. The observed increase with a saturation of ion emission at long delays or long pulse durations result from an interaction between the shaped laser pulse and the expanding matter after the onset of the plasma. Irradiation of boron with long pulses or double pulses reduces the production of nanoparticles, compared to the case of short pulses. Temporal shaping does not significantly affect the nanoparticle temperature, in spite of significant variations in the quantity of the ejected nanoparticles.