Heat-induced darkening and spectral broadening in photodarkened ytterbium-doped fiber under thermal cycling.
We study thermal bleaching of photodarkening-induced loss in a 20-microm core diameter, large-mode-area ytterbium-doped silica fiber. Pristine and photodarkened samples are subjected to thermal cycling pulses. Recovery of the photodarkened fiber absorption coefficient initiates at approximately 350 degrees C and complete recovery is reached at approximately 625 degrees C. However, prior to recovery, the photodarkened fiber exhibits further heat-induced increase of absorption loss. This increase of loss is attributed to both a permanent increase of loss-inducing color centers and a temperature-dependent broadening of the absorption spectrum. Post-irradiation heat-induced formation of color centers suggests the presence of an intermediate energy state in the near-infrared photochemical mechanism for photodarkening.
Söderlund
Mikko J
MJ
Helsinki University of Technology, Tietotie 3, FIN-02015 TKK, Finland. mikko.soderlund@tkk.fi
Montiel i Ponsoda
Joan J
JJ
Koplow
Jeffrey P
JP
Honkanen
Seppo
S
D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006358:Hot Temperature; D055100:Optical Fibers; D017785:Photons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000737:chemistry*; D013057:Spectrum Analysis / Q000295:instrumentation*; D015018:Ytterbium / Q000737:chemistry*
D012822:Silicon Dioxide; D015018:Ytterbium