Nanosecond Laser Ablation: Mathematical Models, Computational Algorithms, Modeling

Abstract

The basic mathematical models, computational algorithms, and results of mathematical modeling of various modes of laser action on metals are considered. It is shown that for mathematical description and analysis of the processes of laser heating, melting, and evaporation of condensed media, various theoretical approaches are used: continuum, kinetic, atomistic, etc. Each of them has its own field of applicability, its advantages, and disadvantages. Mathematical description of ns-laser ablation is usually carried out within the framework of continuum approach in the form of hydrodynamic models that take into account reaction of irradiated material to varying density, pressure, and energy both in the target and in the vapor-gas medium. Within the framework of continuum approach, a multiphase, multifront hydrodynamic model and computational algorithm were constructed that were designed for modeling ns-PLA of metal targets embedded in gaseous media. It is shown that proposed model and computational algorithm allow to carry out the simulation of interrelated mechanisms of heterogeneous and homogeneous evaporation of metals manifested as a series of explosive boiling. Modeling has shown that explosive boiling in metals occurs due to the presence of a near-surface temperature maximum. It has been established that in ns-PLA, exposure regimes can be realized in which a phase explosion is the main mechanism of material removal. The verification of reliability of obtained results was carried out by comparing experimental data and calculations with atomistic models.

Atomic understanding of structural deformations upon ablation of graphene

“…When the laser pulse is ultrafast, these processes are temporally decoupled; therefore, we can study them separately as excitation, energy transfer, and material removal processes. [24] A number of previous studies utilizing analytical approaches have provided an understanding of the energy transfer during the ablation process at a macroscopic level; for example, continuum and hydrodynamic models, [25][26][27][28][29][30][31] finite element simulations, [32] time-dependent Schrödinger equation, [33] ) and twotemperature models. [24,[34][35][36][37] While such studies provide important insight for controlling the ablation rate, to precisely control the shape and size of hole formation, it is beneficial to study and understand the mechanisms on the atomic scale; that is, the breaking and re-forming of the strong carbon-carbon bonds.…”

Atomistic modeling of crystal-melt interface mobility of fcc (Al, Cu) and bcc (Fe) metals in STRONG superheating/undercooling states

“…Recent use of ultrashort fs, ps -laser pulses to achieve deep undercooling in melts of thin (10-50 nm) metal films [23][24][25][26][27] has brought to the fore the study of bulk and surface mechanisms of melting of solids [43,44]. The degree of undercooling during solidification can be easily controlled by varying the thickness of the thin films.…”

Machine learning for multi-dimensional optimisation and predictive visualisation of laser machining

“…starting from equations that accurately describe all interactions between light and matter) then the optimal parameter configuration could theoretically be determined directly, without the need for any experimental optimisation. Unfortunately this approach is generally not effective, as many approximations have to be made to simplify such modelling and simulations of light-matter interaction rapidly become computationally intractable when the model size is increased to represent experimentally useful scale dimensions (Mazhukin 2017). It is also challenging to include subtle effects such as imperfections in the beam quality or sample surface in such a simulation (Otto et al 2012).…”