Continuum models of ultra-short laser ablation

Bulgakova, N.M. (2012) Continuum models of ultra-short laser ablation. 3rd Int School on Lasers in Materials Science, Venice, Italy. 07 - 14 Jul 2012.

Record type: Conference or Workshop Item (Other)

Abstract

Femtosecond laser pulses provide unique possibilities for high-precision material processing. Due to rapid energy delivery, heat-affected zones in the irradiated targets are strongly localized with minimal residual damage that allows generation of well-defined microstructures with high quality and reproducibility. Understanding of the underlying physics and interrelation of the processes taking place in materials irradiated by ultrashort laser pulses may facilitate optimization of experimental parameters in current applications and development of contemporary pulsed laser technologies. The complexity of the interrelated processes involved in laser-matter interaction gives rise to elaboration of theoretical and computational descriptions of the phenomenon basing on different approaches including atomistic and continuum ones. Atomistic modeling based on molecular dynamics approaches has a great potential, being however still strongly limited to description of a relatively small amount of matter as compared to that involved into laser - solid interaction. Continuum models applied to small spatial and temporal scales of laser-irradiated matter may be rather crude as they strongly simplify a number of processes and their interrelations. However, being properly applied and treated, continuum considerations may provide valuable insights into the extremely complicated phenomenon of the interaction of light with matter.
In this lecture a number of continuum models will be presented which have been successfully applied to describe response of different materials to ultrashort laser irradiation. The details of a unified continuum model developed for studying charge-carrier transport in metals, semiconductors, and dielectrics exposed to femtosecond laser radiation will be analyzed. Based on a drift-diffusion approach, this model allows to elucidate the dynamics of the electric field generated in the target due to photo-emission and to get insight into the origin of the Coulomb explosion process. The advantages and limitations of the model, time and length scales of its application, and modifications for different classes of materials will be analyzed and its extension to other systems such as carbon nanotubes will be demonstrated. The other examples of the continuum models will be presented, a two-dimensional model of surface layer breakdown in wide-band-gap dielectric materials which has made possible to uncover mechanisms that enable the spatial modulation of the surface structures induced by temporally modulated laser pulses, and a combined thermal/elasto-plastic model which has allowed to uncover the mechanisms and dynamics of microbump and nanojet formation on nanosized gold films under femtosecond laser irradiation. In addition, a novel modeling approach will be demonstrated which has been developed for studying the spatiotemporal dynamics of ultrashort-laser-induced modifications inside transparent materials. The approach is based on the Maxwell equations for describing laser light propagation through a dielectric sample and light absorption in the focal volume and on the equations of thermo-elasto-plasticity for simulating laser-induced material heating and expansion/compaction dynamics.

This record has no associated files available for download.