Multi-physic simulation in the laser sources

As lasers become more and more powerful and energetic, thermo-optical effects and mechanical constraints can no longer be neglected, and numerous thermal, mechanical and hydraulic specialists must be called in. However, multiphysics simulation codes enable the laser engineer to design a laser system without having to call on an external specialist, at least in the dimensioning phase. These codes avoid the tedious task of transferring data files from one specialized software package to another, since the same interface and input data feed several physics calculations at once. The laser engineer thus becomes capable of choosing the materials that will hold the optics, and translating optical specifications into mechanical and cooling specifications that can be understood by a mechanical design office with no optical skills. The classic example is the thermal lens. Non-uniform temperature rise in laser components leads to undesirable beam convergence effects. The laserist sees thermal lensing effects, but has difficulty translating this into mechanical deformations, and doesn't know how to design the cooling to limit them. Conversely, the thermomechanic is unable to grasp the notion of optical lens or optical wave surface deformation, as the mechanical precision required for lasers is at the very limit of his field. However, fine-tuning the cooling geometry and optical retention can often limit the problem.

The aim of this article is to explain what a multiphysics code is, and to present its advantages for the design of laser systems. The basics presented will save the beginner time in understanding and using these tools. The thermal, mechanical and fluid mechanics calculation modules are described, along with their main parameters. Two examples of laser component optimization illustrate the benefits of these codes for the laserist.

At the end of the article, readers will find a glossary and a table of symbols used.