Abstract
Melting and ablation with an ultrashort laser pulse have been widely used for a variety of applications.
The mechanisms of melting and ablation are strongly dependent on the material and photoexcitation
levels. Using high peak power laser fluences induces nonthermal processes that involve nonthermal
melting, cold ablation and plasma formation; however, thermal related processes are dominant at
relatively a low laser fluence. In this paper, we summarize the laser melting and ablation processes from
the viewpoint of time-resolved structural studies and introduce the development of a femtosecond timeresolved
electron diffraction setup. We also show a time-resolved electron diffraction experiment to
study the evolution of the ablation process that follows femtosecond 400-nm laser excitation in
crystalline potassium iodide. Our results reveal fast electronic and localized structural changes that lead
to the ejection of particles, reflecting the very nature of the strong repulsive forces at play.
