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Origin and evolution of phase-shifts in high-power fiber laser systems: detailed insights into TMI
Author(s): Cesar Jauregui; Christoph Stihler; Andreas Tünnermann; Jens Limpert
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Paper Abstract

In this work, we study the generation and evolution of phase-shifts between the modal interference pattern and the thermally-induced index grating due to pump-power changes. This study is not only important to understand new mitigation strategies based on controlling such phase-shifts, but also to comprehend how pump/signal noise can trigger TMI. Understanding how such a phase-shift can develop from a pump/signal change is not trivial, since the movement of both the MIP and the RIG are thermally driven and, therefore, should have similar time constants. Our simulations show unequivocally that a change of the pump power will lead to the generation of a phase-shift and the physical reason for this behavior is unveiled. The main reason is an increased sensitivity of the MIP to temperature variations because the local beat-length changes of the MIP are accumulated along the whole fiber length. Therefore, the further downstream the fiber a MIP maximum is (i.e. closer to the pump end in a counter-pumped configuration), the stronger and faster its position shift will be. This insight shows a way to obtain more TMI-resilient fiber designs and may help understanding the core area dependence of TMI.

Paper Details

Date Published: 7 March 2019
PDF: 6 pages
Proc. SPIE 10897, Fiber Lasers XVI: Technology and Systems, 1089704 (7 March 2019); doi: 10.1117/12.2508854
Show Author Affiliations
Cesar Jauregui, Friedrich-Schiller-Univ. Jena (Germany)
Christoph Stihler, Friedrich-Schiller-Univ. Jena (Germany)
Andreas Tünnermann, Friedrich-Schiller-Univ. Jena (Germany)
Helmholtz-Institute Jena (Germany)
Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Jens Limpert, Friedrich-Schiller-Univ. Jena (Germany)
Helmholtz-Institute Jena (Germany)
Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)


Published in SPIE Proceedings Vol. 10897:
Fiber Lasers XVI: Technology and Systems
Adrian L. Carter; Liang Dong, Editor(s)

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