title: Cooperative luminescence and absorption in Ytterbium-doped silica fiber and the fiber nonlinear transmission coefficient at lambda=980 nm with a regard to the Ytterbium ion-pairs' effect.
abstract: An experimental and theoretical investigation of the nonlinear transmission coefficient in a set of Ytterbium-doped silica fibers (YFs) with various concentrations of Yb(3+) ions at continuous-wave 980-nm pumping is reported. An analysis of the obtained experimental data shows that YF transmission coefficient is notably affected by the presence of Yb(3+) - Yb(3+) ion-pairs in the fibers, especially in heavily-doped ones. The last fact is confirmed by the study of the cooperative luminescence and absorption effects in the fibers, where a detailed inspection of their dependence on Yb3+ concentration is presented. The pairs' effect is shown to seriously modify both the nonlinear character of YF transmission coefficient at lambda = 980 nm and Yb(3+) excited-state relaxation. A modeling of the experimental data is performed, which allows to find the coefficients addressing the pairs' effect in each of YFs under study and, as a result, to fit the experimentally measured dependences of YF transmission coefficient on pump power, fiber length, and Yb(3+) concentration.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Kir'yanov
authors.forename: Yuri O
authors.initials: YO
authors.lastname: Barmenkov
authors.forename: Itzel L
authors.initials: IL
authors.lastname: Martinez
authors.forename: Audrey S
authors.initials: AS
authors.lastname: Kurkov
authors.forename: Evgenii M
authors.initials: EM
authors.lastname: Dianov