Ultrashort pulse surface melting and smoothing: The impact of pulse spacing on heat accumulation and structure formation

Ultrashort laser pulses are often used in industrial manufacturing due to the small heat-affected zones they produce and their low melt formation. A contrasting approach aims to exploit the residual heat of successively applied laser pulses in combination with the material response. As a result of the heat accumulation within a burst, the formation of a melt film that is highly spatially and temporally confined is possible. Experiments, theoretical analysis, and numerical heat-flow simulations are used to show the influence of the laser parameters on pulsed melting and surface structure formation. Special attention is paid to the temporal delay between the pulses. A comparison of the process on iron and titanium allows the influence of material properties to be considered.