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Influence of pedestal diameter on mode instabilities in Yb/Ce/Al-doped fibers

 
: Möller, F.; Distler, V.; Walbaum, T.; Haarlammert, N.; Nold, J.; Schreiber, T.; Unger, S.; Reichel, V.; Kobelke, J.; Bierlich, J.; Schwuchow, A.; Eschrich, T.; Leich, M.; Wondraczek, K.; Tünnermann, A.

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Volltext ()

Optics Express 28 (2020), Nr.22, S.33456-33474
ISSN: 1094-4087
Englisch
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IOF ()
continuous wave; counter-pumped amplifiers; diffraction-limited beams; fiber optic; mode instabilities

Abstract
In this paper we present numerical and experimental results revealing that the mode instability threshold of highly Yb-doped, Ce/Al co-doped pedestal fibers is affected by the size of the index-increased pedestal structure surrounding the core. An alternative preparation technology for the realization of large mode area fibers with very large Al-doped silica pedestals is introduced. Three different pedestal fiber design iterations characterized by low photo darkening were manufactured and tested in counter-pumped amplifier setups. Up to 1.9 kW continuous wave output power of near-diffraction-limited beam quality (M2 = 1.26) was achieved with an 18/200/420 μm fiber of very low NA = 0.042, limited only by the occurrence of mode instabilities.

: http://publica.fraunhofer.de/dokumente/N-608681.html