Reversible photo-darkening and resonant photobleaching of Ytterbium-doped silica fiber at in-core 977-nm and 543-nm irradiation
✍ Scribed by A.D. Guzman Chávez; A.V. Kir'yanov; Yu.O. Barmenkov; N.N. Il'ichev
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 415 KB
- Volume
- 4
- Category
- Article
- ISSN
- 1612-2011
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✦ Synopsis
We report experimental results showing novel features in photo-darkening and photo-bleaching of a heavily-doped Ytterbium silica fiber exposed to in-core 977-nm and 543-nm irradiation. It is shown that pumping of the fiber at the resonant 977-nm wavelength leads to an increase of absorption in the spectrally wide range (400–1000 nm, photo-darkening) and a simultaneous decrease of the resonant (Yb^3+^) absorption coefficient near ∼ 1 μm (resonant photo-bleaching). Such a character of the Ytterbium fiber spectra transformations allows us to propose that they are a signature of the 977-nm light-induced Yb^3+^ → Yb^2+^ conversion process, with the spectrally wide absorption, or photo-darkening, to arise owing to the Yb^2+^ centers formation and the resonant photo-bleaching to stem from the corresponding decrease of Yb^3+^ ions concentration. It is as well demonstrated that an exposure of the Ytterbium fiber, where the aforementioned transformations have occurred, to the 543-nm light results in a partial return of the initial fiber properties – bleaching of the spectrally wide excess loss in the visible and increasing of the resonant 977-nm (Yb^3+^) absorption peak. Therefore, we reveal a reverse process, Yb^2+^ → Yb^3+^, possibly taking place in the last case.