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Experimental Comparison of Fundamental Mode Content in Er:Yb-Codoped LMA Fibers With Multifilament- and Pedestal-Design Cores

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V. Kuhn, S. Unger, S. Jetschke, D. Kracht, J. Neumann, J. Kirchhof, P. Weßels
Experimental Comparison of Fundamental Mode Content in Er:Yb-Codoped LMA Fibers With Multifilament- and Pedestal-Design Cores
Journal of Lightwave Technology 22 (28), 3212–3219 (2010)
Publication type: Journal Article (reviewed)
DOI: 10.1109/JLT.2010.2088378

Abstract

We report on fundamental mode content measurements performed on single-frequency large mode area fiber amplifiers based on Er:Yb-codoped multifilament-core (MFC) and step-index pedestal-design fibers. The mode content of the amplifier output was analyzed with respect to free-space TEM modes using a nonconfocal scanning ring cavity. At power levels of several watts, the commercial step-index pedestal-design fibers with respective core diameters of 23 and 25 m showed a mode content exceeding 80%. However, a mode content of up to 95% could be obtained with an MFC fiber also with larger core diameter of 31/28 m in hexagonal shape. To the best of our knowledge, we utilized the nonconfocal scanning ring cavity technique for the first time in the wavelength region of 1.5 m and additionally for the first time on fibers with pedestal as well as MFC design.