title: Evidence of Tm impact in low-photodarkening Yb-doped fibers.
abstract: In contrast to Yb/Al-doped fibers, the influence of very low Tm(2)O(3) concentrations (≥ 0.1 mol-ppm) on photodarkening (PD) is clearly detectable in Yb/P-doped fibers that are known to show little degradation effects. For Tm(2)O(3) additions of more than 50 mol-ppm, the measured PD loss is even similar to Yb/Al-doped fibers with comparable rare earth concentrations. Our work reveals the risk of color center generation by pumping at wavelengths of 915 nm or 976 nm even in Al-free Yb-doped fibers and emphasizes the importance of high purity of raw materials for the preparation of Yb laser fibers with expected very low PD.
authors.affiliation: Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany. sylvia.jetschke@ipht-jena.de
authors.forename: Sylvia
authors.initials: S
authors.lastname: Jetschke
authors.forename: Sonja
authors.initials: S
authors.lastname: Unger
authors.forename: Anka
authors.initials: A
authors.lastname: Schwuchow
authors.forename: Martin
authors.initials: M
authors.lastname: Leich
authors.forename: Julia
authors.initials: J
authors.lastname: Fiebrandt
authors.forename: Matthias
authors.initials: M
authors.lastname: Jäger
authors.forename: Johannes
authors.initials: J
authors.lastname: Kirchhof
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D008027:Light; D012542:Scattering, Radiation; D013932:Thulium / Q000737:chemistry*; D015018:Ytterbium / Q000737:chemistry*
chemical_list: D013932:Thulium; D015018:Ytterbium