Experimental and theoretical studies of thermally induced aberrations in optical systems for laser material processing

• Applicants: Professor Dr. Peter Loosen; Professor Dr. Reinhart Poprawe
• Subject Area: Production Automation and Assembly Technology
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 244193730

The development of laser sources towards higher power and improved beam quality enables constantly new applications due to increased power densities and improved focusability. Material processing can be sped up, interaction zones can be reduced and the distance to the workpiece can be enlarged. However, optical elements used for laser beam guiding and shaping are exposed to high thermal loads, which are even increasingly aggravated by the trend for miniaturization. In the consequence, mechanical and optical properties of the elements change. Resulting wave front aberrations of the optical system reduces the beam quality used for the laser processing and also deteriorates an often required optical coaxial process control. The advantages of high brilliant beam sources are thus currently not exhaustively used.The objective of the project proposal is the generation of fundamentals for a coupled multiphysic simulation of thermo-optical influences onto the imaging quality of optical systems for high power laser systems. Thus, the design of optical systems shall be enabled which are robust against thermal disturbance factors. Therefore, an algorithmic coupling of ray tracing and finite element analysis (FEA) is required, in order to enable the simulation of thermally induced wave front aberrations based on characterized glass materials, coatings, mounts and further components. The most important scientific research questions address the determination of energy input and output, the algorithmic interpolation of discret numerical results for providing FEA results in ray tracing simulation and the computation of thermally induced wave front deformations. If a robust model can be developed, steps towards optimization, computation of transient behavior and compensation of thermal effects can be taken.

• DFG Programme: Research Grants