title: High-power thermally guiding index-antiguiding-core fibers.
abstract: We investigate high-power operation of a very-large-mode-area (VLMA) fiber concept based on an index-antiguiding, thermally guiding core in which an ytterbium-doped region is completely surrounded by silica with a slightly higher refractive index. Experimentally, regimes of antiguidance, single-mode operation, and mode instabilities predominantly with radially symmetric higher-order modes are observed. Fundamental limitations for conventional VLMA step-index fibers are discussed.
authors: Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Albert-Einstein-Strasse 15, Jena 07745, Germany. jansen@iap.uni‑jena.de
authors: Florian
authors: F
authors: Jansen
authors: Fabian
authors: F
authors: Stutzki
authors: Hans-Jürgen
authors: HJ
authors: Otto
authors: Cesar
authors: C
authors: Jauregui
authors: Jens
authors: J
authors: Limpert
authors: Andreas
authors: A
authors: Tünnermann