Shorter Than the Blink of an Eye – Simulation of fs-Lasers for Material Processing

The development of femtosecond lasers has opened a new era in laser material processing. A great number of breakthroughs has been achieved in medical technology and surface treatment. Multiplex coupled phenomena occurring with ultra-short pulsed laser ablation severely impede process design. Consequently the objective is to develop a three dimensional multi-physics simulation model providing a sound prediction of process results of material treatment by femtosecond lasers.

Comprehensive understanding of the physics of beam-matter interaction and mathematical representation of these processes is a prerequisite. Creation of the simulation model will be based on models for laser machining formerly developed at the institute. The basic software OpenFOAM, opens an external URL in a new window has been modified and expanded for that purpose. Thus simulation of laser ablation with pulses down to 1ns has been made possible. Phase transitions, wetting, fluid dynamics, beam propagation etc. are already contained in the existing model. In order to represent the absorption of ultra-short laser pulses in metals it will be necessary to implement the so-called two-temperature model. Additionally the gaseous phase shall be calculated by the Navier-Stokes equations for compressible media to encompass the shock waves of explosive evaporation.

The chronological and spatial multiscale set of problems with simulation of femtosecond lasers generates vast amounts of data due to chronological and spatial discretisation. Their volume reaches critical size for storage space and causes long calculation times.

The students of the participating schools (HTL-Donaustadt, opens an external URL in a new window, AHS Maria Regina, opens an external URL in a new window) are about to learn about the scientific approach in general and will be challenged to develop a compression algorithm optimised for the special application accordingly, taking into consideration statistical adjacency relations in order to reduce the data volume. The routines to be developed will be integrated in the simulation subsequently.

The compression algorithm developed by the students of HTL Donaustadt is available on the following Github repository, opens an external URL in a new window.