Photodarkening-induced increase of fiber temperature.
We examine the effect of photodarkening-induced pump light absorption on Yb-doped fiber thermal loading. In these experiments, the fiber is cladding pumped at 915nm, air cooled by natural convection, and monitored with a midinfrared thermal camera. The fiber temperature is found to correlate with progressive photodarkening. The maximum observed fiber temperature was 120 degrees C, recorded at a pump power of 10.5W. The observed increase in fiber temperature can be explained by a model that takes into account the combined effects of the Yb-silica quantum defect, the temperature dependence of the Yb-absorption cross section, and photodarkening-induced loss at 915nm. We hypothesize that the latter effect results in the progressive activation of temperature-dependent photochemical processes (e.g., bleaching) and is an important consideration with regard to the accurate modeling of Yb-doped fiber photodarkening kinetics.
Montiel I Ponsoda
Joan J
JJ
Aalto University School of Sciences and Technology, Tietotie 3, 02150 Espoo, Finland. joan.montiel@tkk.fi
Söderlund
Mikko J
MJ
Koplow
Jeffrey P
JP
Koponen
Joona J
JJ
Honkanen
Seppo
S