title: Thermal bleaching of photodarkening-induced loss in ytterbium-doped fibers.
abstract: We study the thermal bleaching process of photodarkening-induced loss in ytterbium-doped fibers. The observed power-law time dependence of the normalized absorption coefficient is well represented by the thermal decay model of Erdogan et al. [J. Appl. Phys. 76, 73 (1994)]. Using this model, we derive the activation energy associated with thermal recovery of the induced loss to prephotodarkened state. For the studied commercial 20 microm core diameter large-mode-area fiber, the energy distribution consists of a single peak, located at 1.32 eV with a FWHM of approximately 0.31 eV. The results presented are of particular importance to understanding photodarkening and bleaching processes in high-power fiber lasers.
authors.affiliation: Helsinki University of Technology, Tietotie 3, FIN-02015 TKK, Helsinki, Finland. mikko.soderlund@tkk.fi
authors.forename: Mikko J
authors.initials: MJ
authors.lastname: Söderlund
authors.forename: Joan J
authors.initials: JJ
authors.lastname: Montiel i Ponsoda
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Koplow
authors.forename: Seppo
authors.initials: S
authors.lastname: Honkanen