Project 3

Dynamic light propagation in high power glas fibre amplifiers

  • Institute: Laser Zentrum Hannover e.V.
  • Principle Investigator: Dr. Peter Weßels, Dr. Dietmar Kracht
  • Researcher: Dr. Sergii Iakushev

Current and future laser applications such as material processing require increasingly higher laser powers, both in the case of continuously emitting and pulsed laser systems. One of the current major problems in the performance scaling of high-power fiber laser systems is transverse mode instabilities (TMI). In this case, the beam profile suddenly begins to fluctuate from a certain power threshold and thus limits the useful maximum output power.

Until now there is no complete explanation of all observed phenomena in a consistent manner. Novel efficient approaches for mitigating of TMI and increasing the power threshold are required. For deeper understanding of mode instabilities phenomenon the development of a complex simulation model of all involved processes is necessary.

This includes propagation of the light field in the active core region of fiber amplifiers under the changes of refractive index due to the population density variation and temperature impact. These processes, which take place on completely different time scales, can currently only be simulated separately.

In this subproject, a simulation model is developed where all these processes and their interaction can be mapped integrally and the observed behavior of fiber amplifiers can be understood.

In addition to understanding the processes that lead to mode instability, the non-linear beam propagation code is also be used for the simulation of non-linear encoders, which can form a basic element (saturable absorber) for the realization of maintenance-free, completely fiber-coupled ultra-short pulse oscillators.

3D BPM simulation of amplification and mode interference in high-power Yb-doped fiber amplifier.