title: Experimental evidence of differences in the absorption spectra of clustered and isolated ions in erbium-doped fibers.
abstract: The absorption spectra of clustered and isolated ions in erbium-doped germanosilicate fibers have been experimentally studied. The ground-state absorption spectra broaden as the degree of erbium-ion clustering increases, indicating that the absorption spectrum of clustered ions is significantly different from that of the homogeneous ions. This fact is confirmed by comparison of the broadened absorption spectra with the fiber's unbleachable loss spectrum, a direct measurement of the clustered ions. This is the first experimental evidence to the authors' knowledge that indicates different absorption cross sections for the two species of ions in germanosilicate glass, an assumption that is used in the theoretical description of self-pulsing in erbium-doped fiber lasers but is in direct contradiction to the pair-induced quenching model widely used to characterize erbium-doped fiber amplifiers.
authors.forename: B N
authors.initials: BN
authors.lastname: Samson
authors.forename: W H
authors.initials: WH
authors.lastname: Loh
authors.forename: J P
authors.initials: JP
authors.lastname: de Sandro