Time-resolved imaging techniques applied to femtosecond laser material processing

Abstract

This article summarizes the motivation, the experimental procedures and the main results of the thesis awarded with the 7th Justianiano Casas Award. Within the thesis, different strategies based on time-resolved microscopy were developed and applied to the study of changes occurring at the surface of materials upon femtosecond laser excitation. First, this optical pump-and-probe technique is applied to the study of the ablation dynamics of lithium niobate, a crystalline dielectric material with numerous applications in optics and photonics. Second, the transformation dynamics of a phosphate glass was investigated upon irradiation with sub-ablative laser pulse fluences, leading to the formation of a permanent heat affected layer. To this end, a fiber-based optical delay line was developed, enabling to explore delays up to 0.5 µs. Third and last, an optical method capable of simultaneously fabricating laser-induced periodic structures and resolving spatially and temporally their formation process is reported. The results presented in this thesis demonstrate the huge potential of time-resolved pump-probe microscopy for revealing the process dynamics of a multitude of material modification processes upon femtosecond laser excitation.