Abstract
The research in the field of laser-induced materials processing is evolving continuously with new inventions in laser technology. This chapter mainly discusses the relevant physical mechanisms of laser ablation based on laser-matter interaction. Femtosecond laser excitation provides suitable conditions for studying the basic processes in irradiated materials, as compared to the duration of these processes, femtosecond laser pulses are sufficiently short. In the process of laser action on the matter, the thermal mechanism, charge carrier removal, thermal and structural effects, and other processes are extremely complex. The ultrashort laser pulse instantly puts the material in a strong nonequilibrium state characterized by hot electrons and cold ions. After the pulse ends, the electron transfers its energy to the ion through electron phonon coupling in sub-picoseconds. This heats up the phonon bath before the slow thermal effect can reconstruct the material. The electron effect plays an important and possibly dominant role in the laser ablation of nonmetallic solid surfaces. This review first describes the mechanism of laser-matter interaction from the perspective of energy, summarizes the electronic excitation and energy relaxation paths of light on semiconductors and dielectric materials, focuses on the electronic excitation and relaxation mechanisms in laser-induced ionization, desorption, and ablation, and finally analyzes the above-mentioned related processes from the perspective of material structure relaxation.