Analysis and manipulation of thermally induced modal instabilities in high-power fiber lasers (Conference Presentation)

Till Walbaum; Friedrich Möller; Maximilian Strecker; Benjamin Yildiz; Stefan Kuhn; Nicoletta Haarlammert; Thomas Schreiber

doi:10.1117/12.2645232

2 November 2022 Analysis and manipulation of thermally induced modal instabilities in high-power fiber lasers (Conference Presentation)

Till Walbaum, Friedrich Möller, Maximilian Strecker, Benjamin Yildiz, Stefan Kuhn, Nicoletta Haarlammert, Thomas Schreiber,

Author Affiliations +

Proceedings Volume 12273, High-Power Lasers and Technologies for Optical Countermeasures; 122730C (2022) https://doi.org/10.1117/12.2645232
Event: SPIE Security + Defence, 2022, Berlin, Germany

Abstract

Defense applications require intrinsically stable and resilient laser systems. Using single- or few-mode output fibers, fiber-based high-power lasers can address these challenges and also feature excellent beam quality, allowing to achieve high power density at long focusing distance. At high power levels, these diffraction limited output beams can be spoiled by thermally induced transverse mode instabilities (TMI), which cause beam profile fluctuations and thus increase the M²-factor. As TMI are an interference-based effect, it is to be expected that there is a dependence on polarization. We have thus set up an analysis setup that allows to characterize the individual mode content of the fluctuating beam along with the full polarization (in terms of Stokes vector) of each individual contributing mode at kHz speed. We will present the setup and first results for high power systems. In order to manipulate the TMI threshold, it has been shown to be beneficial to distribute the heat load evenly along the fiber. On the other hand, monolithic fiber component availability favors a co-propagating pump approach. We will present a dual-tone seeding setup that allows for variable modification of the heat load position and discuss the impact on the TMI threshold.

Conference Presentation

Citation Download Citation

Till Walbaum, Friedrich Möller, Maximilian Strecker, Benjamin Yildiz, Stefan Kuhn, Nicoletta Haarlammert, Thomas Schreiber, and "Analysis and manipulation of thermally induced modal instabilities in high-power fiber lasers (Conference Presentation)", Proc. SPIE 12273, High-Power Lasers and Technologies for Optical Countermeasures, 122730C (2 November 2022); https://doi.org/10.1117/12.2645232

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