Fiber Laser Mode Instabilities

Temporal dynamics of mode instabilities in highpower fiber lasers and amplifiers

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.

Hans-Jürgen Otto,, Fabian Stutzki, Florian Jansen, Tino Eidam,Cesar Jauregui, Jens Limpert and Andreas Tünnermann, 2012
Institute of Applied Physics, Abbe Center of Photonics, Jena, Germany
Helmholtz-Institute Jena, Jena, Germany
Fraunhofer Institute for Applied Optics and Precision Engineering, Jena, Germany

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