title: Temporal dynamics of mode instabilities in high-power fiber lasers and amplifiers.
abstract: The temporal behavior of mode instabilities in active large mode area fibers is experimentally investigated in detail. Thus, apart from the onset threshold of mode instabilities, the output beam is characterized using both high-speed camera measurements with 20,000 frames per second and photodiode traces. Based on these measurements, an empiric definition of the power threshold of mode instabilities is introduced. Additionally, it is shown that the temporal dynamics show a transition zone between the stable and the unstable regimes where well-defined periodic temporal fluctuations on ms-timescale can be observed. Finally, it is experimentally shown that the larger the mode-field area, the slower the mode-instability fluctuation is. The observations support the thermal origin of mode instabilities.
authors: Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Albert-Einstein-Str. 15, 07745 Jena, Germany. hans-juergen.otto@uni-jena.de
authors: Hans-Jürgen
authors: HJ
authors: Otto
authors: Fabian
authors: F
authors: Stutzki
authors: Florian
authors: F
authors: Jansen
authors: Tino
authors: T
authors: Eidam
authors: Cesar
authors: C
authors: Jauregui
authors: Jens
authors: J
authors: Limpert
authors: Andreas
authors: A
authors: Tünnermann