title: Evidence of AlOHC responsible for the radiation-induced darkening in Yb doped fiber.
abstract: Using a combination of experimental techniques such as optical absorption, Raman scattering, continuous wave and pulse Electron Spin Resonance (ESR), we characterize a set of γ-irradiated Yb(3+) doped silica glass preforms with different contents of phosphorous and aluminum. We demonstrate that when P is introduced in excess compared to Al, nearly no radiodarkening is induced by γ-rays. On the other hand, when Al>P, a large absorption band is induced by radiation. Thermal annealing experiments reveal the correlation between the decrease of the optical absorption band and the decrease of the Al-Oxygen Hole Center (AlOHC) ESR signal, demonstrating the main role of AlOHC defects in the fiber darkening. HYSCORE (HYperfine Sublevel CORElation) pulse-ESR experiments show a high Al-P nuclear spin coupling when P>Al and no coupling when Al>P. This result suggests that both AlOHC and POHC creation is inhibited by Al-O-P linkages. Confronting our data with previous works, we show that the well-known photodarkening process, meaning losses induced by the IR pump, can also be explained in this framework.
authors.affiliation: Laboratoire des Solides Irradiés, UMR 7642, CEA-CNRS-Ecole Polytechnique, 91128 Palaiseau, France. thierry.deschamps@polytechnique.edu
authors.forename: Thierry
authors.initials: T
authors.lastname: Deschamps
authors.forename: Hervé
authors.initials: H
authors.lastname: Vezin
authors.forename: Cédric
authors.initials: C
authors.lastname: Gonnet
authors.forename: Nadège
authors.initials: N
authors.lastname: Ollier
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D010100:Oxygen / Q000737:chemistry*; D015018:Ytterbium / Q000737:chemistry*
chemical_list: D000535:Aluminum; D015018:Ytterbium; D010100:Oxygen