Open AccessPhotodarkening in Yb doped fibers: experimental evidence of equilibrium states depending on the pump power
Author(s) -
Sylvia Jetschke,
Sonja Unger,
U. Röpke,
J. Kirchhof
Publication year - 2007
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.15.014838
Subject(s) - photodarkening , materials science , ion , excited state , optics , doping , optical pumping , cladding (metalworking) , atomic physics , fiber laser , optical fiber , laser , optoelectronics , chemistry , physics , organic chemistry , metallurgy
Photodarkening in Yb doped fibers was examined at 633 nm in-situ during cladding pumping at 915 nm with varying pump powers and with no indication of an onset threshold. For the first time, the partial bleaching of the photodarkening loss by the pump power itself was observed. We found the relaxation to well-defined equilibrium states of the core excess loss, depending on the Yb inversion. From the dependence of the measured rate constant on the density of excited Yb ions we conclude, that on average 3 to 4 excited Yb ions create or bleach one color center responsible for the core excess loss.