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Highly scalable femtosecond coherent beam combining system of high power fiber amplifiers

Anke Heilmann (LULI)

Future applications of high power ultrafast laser systems require simultaneously high average and peak powers. A technique which has proved to be capable of meeting these demands is coherent beam combining (CBC).

In this technique, the beam is spatially split prior to amplification, and coherently recombined in one single beam afterwards. In order to achieve an efficient recombination, the spatial and spectral properties of all beams need to be perfectly matched.

For applications such as particle acceleration, the coherent combining of several thousands of fibers needs to be considered. It is thus necessary to investigate highly scalable CBC architectures.

The XCAN project aims at a first demonstration of such a scalable setup by coherently combining 61 fiber amplifiers. In order to study the scientific and technical challenges of such a system, a downscaled version consisting of seven fibers has been implemented.

The design and characterization of this prototype is the subject of this thesis. As a starting point, numerical simulations have been performed in order to estimate the maximum tolerable mismatches between the spatial and spectral properties of the beams.

Based on this modeling work, a seven fiber CBC system has been assembled and characterized. The obtained results are very promising and imply that our setup is well suited for the accommodation of all 61 fibers of the final XCAN demonstrator.