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Proceedings Paper

Relations between phosphorus/aluminum concentration ratio and photodarkening rate and loss in Yb-doped silica fibers
Author(s): Pierre Laperle; Louis Desbiens; Huimin Zheng; Mathieu Drolet; Antoine Proulx; Yves Taillon
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Paper Abstract

The relations between dopant concentrations (phosphorus and aluminum) and photodarkening rate, excess loss, and activation energies in ytterbium-doped silica fibers are experimentally investigated. It is shown that increasing the concentration of phosphorus from 0.2 to 2.5 mol% in phosphorus/aluminum codoped fiber cores decreases the photodarkening excess loss by a factor of 8 and the photodarkening rate by a factor of 10. Moreover, the effective number of ytterbium ions involved in the photodarkening process increases from 4 to more than 6 for tested phosphorus/aluminum concentration ratios varying from 0.1 to 1 respectively. In contrast, increasing the aluminum concentration from 2 to 5 mol% for a fixed phosphorus concentration of 0.2 mol% has negligible effect on the initial photodarkening rate or the effective number of ytterbium ions involved in the process, but still decreases the photodarkening excess loss by a factor of 5. Those results suggest photodarkening activation energies of 5.2 eV for ytterbium/aluminum-codoped silica fibers and more than 7.8 eV for ytterbium/phosphorus/aluminum-codoped silica fibers. The net improvement in photodegradation of fiber amplifiers based on such phosphorus and aluminum codoping is measured experimentally and numerically simulated. The output power loss of 1064-nm ytterbium-doped LMA fiber amplifiers with phosphorus/aluminum ratios of 0.1 and 0.6 is reduced after 10 000 hours from 17% to less than 2%, respectively. Better understanding of the effects of phosphorus and aluminum on photodarkening will help to design reliable and efficient ytterbium-doped fiber amplifiers.

Paper Details

Date Published: 17 February 2010
PDF: 8 pages
Proc. SPIE 7580, Fiber Lasers VII: Technology, Systems, and Applications, 75801Y (17 February 2010); doi: 10.1117/12.840026
Show Author Affiliations
Pierre Laperle, INO (Canada)
Louis Desbiens, INO (Canada)
Huimin Zheng, INO (Canada)
Mathieu Drolet, INO (Canada)
Antoine Proulx, INO (Canada)
Yves Taillon, INO (Canada)

Published in SPIE Proceedings Vol. 7580:
Fiber Lasers VII: Technology, Systems, and Applications
Kanishka Tankala, Editor(s)

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