Journal article
Photo darkening of rare earth doped silica
The photo darkening (PD) absorption spectra from unseeded amplifier operation (by 915 nm pumping) of ytterbium/aluminum and codoped silica fibers is after prolonged operation observed to develop a characteristic line at 2.6 eV (477 nm). This line is proposed to be due to inter center excitation transfer from type II oxygen deficiency centers ODC(II) to Tm3+ trace impurities.
The ODC(II) is proposed to be the result of a displacive transition of a 4-fold silica ring hosting two 3-fold silicon units that presents two non-bridging oxygen to Yb3+ (as part of its 6-fold coordination by oxygen). The displacive transition is initiated by a charge disproportionation process which leads to NBO transfer in forming dioxasilirane (2-fold coordinated silicon with two NBO attached) next to silylene (2-fold coordinated silicon with a lone electron pair).
In collaboration with a valence electron of Yb 3+ a new 1/2/11/2 chemical bond is formed on dioxasilirane which comprises the PD color center for the visible and near-infrared. Difference in solid acidity of the silica material co-doped with Yb/Al and Yb/P may explain the observed difference in spectral shapes by change of bond order to the formed chemical bond. © 2011 Optical Society of America.
Language: | English |
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Year: | 2011 |
Pages: | 19797-19812 |
ISSN: | 10944087 |
Types: | Journal article |
DOI: | 10.1364/OE.19.019797 |