**1. Introduction**

As diverse as laser applications are, they have one thing in common: the complexity of the interaction of photons with matter and the multiphysics nature of the phenomena (thermal, fluidic, optical, mechanics, etc.) involved during laser processing whether it is drilling [1], grooving [2], cutting [3], welding [4], estimating ablation threshold limits [5] or simply predicting the thermal effects on the material [6]. Several mechanisms can be involved before, during and after the material ejection and they strongly depend on the laser characteristics (wavelength, pulse duration, beam shape, polarization, etc.) and the process parameters (scanning speed, repetition rate, pulse energy, etc.). The development in computer sciences (calculation capability and software) gave the opportunity to better understand the prepon‐ derance or the concomitance of mechanisms depending on the application and the objective of the researcher. Moreover, given the dynamic and short time-scale nature of the laser

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

process, numerical simulation can give an insight of what is happening inside the work‐ piece, which is delicate by experimental means.

Multiphysics packages such as ANSYS, ABAQUS, ADINA, or COMSOL are effective for the aforementioned issue and for fundamental investigation. In the industry, another semiempir‐ ical modeling method is useful when direct answers are expected regarding parameters optimization, predicting the system behavior or analyzing the effect of a modification. The Design Of Experiment (DOE) methodology shows its efficiency especially when the experi‐ mental investigation suffers from constraints such as the availability of the device, the experimenter, the material, the risks, the costs, or the environment.

Although nonexhaustive, a list of laser applications and how they were modeled will be presented in the following parts. Multiphysics models will be presented first, followed by the DOE approach. A laser application will be discussed for both types of numerical simulations.
