title: The influence of index-depressions in core-pumped Yb-doped large pitch fibers.
abstract: Rare-earth doped photonic crystal fibers rely ideally on an index matching of the doped core to the surrounding glass to work properly. Obtaining a perfect index matching is technologically very challenging, and fiber manufacturers opt for targeting an index depression instead, which still ensures the influence of the photonic structure on the light propagation. In this paper the analysis of the influence of this core index depression on the higher-order mode discrimination and on the beam quality of the fundamental mode of different designs of core-pumped active large pitch photonic crystal fibers is discussed. The most promising design is evaluated in terms of mode area scaling with a view to mode field diameters above 100 µm. Detailed requirements on the accuracy of the core index matching are deduced.
authors.affiliation: Institute of Applied Physics, Friedrich-Schiller-University of Jena, Jena, Germany. jansen@iap.uni-jena.de
authors.forename: Florian
authors.initials: F
authors.lastname: Jansen
authors.forename: Fabian
authors.initials: F
authors.lastname: Stutzki
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Otto
authors.forename: Martin
authors.initials: M
authors.lastname: Baumgartl
authors.forename: Cesar
authors.initials: C
authors.lastname: Jauregui
authors.forename: Jens
authors.initials: J
authors.lastname: Limpert
authors.forename: Andreas
authors.initials: A
authors.lastname: Tünnermann
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D008027:Light; D008962:Models, Theoretical; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation; D015018:Ytterbium / Q000737:chemistry*
chemical_list: D015018:Ytterbium