2. Physical mechanisms of ablation

We have reviewed a number of significant parameters for ultra-short processes and described the main pulse absorption mechanisms, enabling us to introduce the specificity of femtosecond pulses. In what follows, we will focus on a more precise description of the mechanisms by which the absorbed energy relaxes, usually leading to ablation of the irradiated material. Of course, most scientific results in this field concern simple materials that are well known in the literature. If we consider industrial applications, the materials of interest take on a complex structure (alloys, for example) and are often confidential. It is therefore difficult to make the link between understanding fundamental ablation mechanisms and process control. However, given the specific nature of laser-matter interaction in femtosecond mode, this fundamental knowledge is still very useful for understanding the challenges...