TMI-threshold investigations of low NA Yb-doped single mode fibers (Conference Presentation)

Franz Beier; Friedrich Möller; Johannes Nold; Bettina Sattler; Stefan Kuhn; Christian Hupel; Sigrun Hein; Andreas Liem; Nicoletta Haarlammert; Thomas Schreiber; Ramona Eberhardt; Andreas Tünnermann

doi:10.1117/12.2287699

14 March 2018 TMI-threshold investigations of low NA Yb-doped single mode fibers (Conference Presentation)

Franz Beier, Friedrich Möller, Johannes Nold, Bettina Sattler, Stefan Kuhn, Christian Hupel, Sigrun Hein, Andreas Liem, Nicoletta Haarlammert, Thomas Schreiber, Ramona Eberhardt, Andreas Tünnermann

Author Affiliations +

Proceedings Volume 10512, Fiber Lasers XV: Technology and Systems; 1051203 (2018) https://doi.org/10.1117/12.2287699
Event: SPIE LASE, 2018, San Francisco, California, United States

Abstract

With their advantages like good beam quality, easy thermal management, high robustness and compact size, fiber lasers are one of the most promising solid state laser concepts for high power scaling with excellent beam quality. One issue of further power scaling is the reduction of nonlinear effects, especially Raman scattering, which consequently led to increased mode field areas. However, for large mode area fibers, new challenges, namely transversal mode instabilities (TMI) have to be taken into account. Beside our investigations in the power scaling of ytterbium doped fiber amplifiers up to 4.4kW output power, we present our investigations of the TMI threshold in dependence on bend diameter and absorption length of a well-known, commercial fiber. Within this scope, we used a 13m piece of the fiber and gradually reduced the bend diameter from 60cm slightly below 14cm within a pump wavelength of 976nm. Furthermore, we increased the fiber length to 30 m, presuming the bend diameter of 14 cm and all experimental conditions. However, in a next step, we detuned the pump wavelength up to 980 nm in order to increase the pump absorption length As a result, we achieved 2.9kW of single mode output at a bend diameter of 14cm. The 4.4kW result was obtained with a separately manufactured low-NA fiber, allowing for a slope efficiency of 90% with regards to the absorbed pump light and an extremely temporal stability.

Conference Presentation

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Franz Beier, Friedrich Möller, Johannes Nold, Bettina Sattler, Stefan Kuhn, Christian Hupel, Sigrun Hein, Andreas Liem, Nicoletta Haarlammert, Thomas Schreiber, Ramona Eberhardt, and Andreas Tünnermann "TMI-threshold investigations of low NA Yb-doped single mode fibers (Conference Presentation)", Proc. SPIE 10512, Fiber Lasers XV: Technology and Systems, 1051203 (14 March 2018); https://doi.org/10.1117/12.2287699

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KEYWORDS

Fiber amplifiers

Absorption

Fiber lasers

Manufacturing

Single mode fibers

Solid state lasers

Thermal effects

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