Simulation and compensation of thermal lensing in high-power optical systems

Abstract

High-power laser beams are usually imaged with the help of suitable optics, consisting of several optical elements. The propagation of such high-power beams can result in a significant thermally induced focus shift, the thermal lens effect. This is mainly due to the deposited power of the beam itself, acting as a heat source in the optical elements. The resulting change in temperature leads to both, a deformation of the optical element, and a change of the refractive index. In this work, the finite element method was coupled with ray tracing, in order to get both, optical and thermal-structural simulation results. Additionally, thermal radiation and the mutual influence of optical elements have to be considered. With the method proposed, the thermal lens of optical systems can be determined exactly, but it also enables for designing of new methods to completely compensate for thermal lensing. In this work, a complete compensation of thermal lensing for a F-θ-scanner could be simulated, which even works at optical powers of 10k<i>W</i>.