Relations between phosphorus/aluminum concentration ratio and photodarkening rate and loss in Yb-doped silica fibers

Pierre Laperle; Louis Desbiens; Huimin Zheng; Mathieu Drolet; Antoine Proulx; Yves Taillon

doi:10.1117/12.840026

17 February 2010 Relations between phosphorus/aluminum concentration ratio and photodarkening rate and loss in Yb-doped silica fibers

Pierre Laperle, Louis Desbiens, Huimin Zheng, Mathieu Drolet, Antoine Proulx, Yves Taillon

Author Affiliations +

Proceedings Volume 7580, Fiber Lasers VII: Technology, Systems, and Applications; 75801Y (2010) https://doi.org/10.1117/12.840026
Event: SPIE LASE, 2010, San Francisco, California, United States

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.

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Pierre Laperle, Louis Desbiens, Huimin Zheng, Mathieu Drolet, Antoine Proulx, and Yves Taillon "Relations between phosphorus/aluminum concentration ratio and photodarkening rate and loss in Yb-doped silica fibers", Proc. SPIE 7580, Fiber Lasers VII: Technology, Systems, and Applications, 75801Y (17 February 2010); https://doi.org/10.1117/12.840026

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