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Proceedings Paper

High-power fiber amplifier using a depressed-clad Yb-doped LMA fiber with low photodarkening
Author(s): Mathieu Drolet; Pierre Laperle; Claude Paré; Huimin Zheng; Louis Desbiens; Antoine Proulx; Yves Taillon
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Paper Abstract

A 225-μJ polarization maintaining ytterbium-doped large-mode-area multiclad fiber was designed and fabricated with an effective mode area of 450 μm2 and a photodarkening maximum excess loss of ~1 dB/m at 1064 nm. The fiber index profile is based on a depressed-clad to obtain a diffraction-limited output. Optimization for low photodarkening and high conversion efficiency while maintaining a good control on the core's refractive index profile has been achieved by adjusting the ytterbium/phosphorus/aluminum concentrations in the fiber core. Concentration ratios of phosphorus/aluminum from 0.12 to 1.25 were experimentally investigated in terms of photodarkening rate and excess loss. Within this range, the photodarkening excess loss was observed to decrease by a factor of 8. The large-mode-area fiber was used in a 10-ns pulse amplifier at 1064 nm with a repetition rate of 100 kHz and 0.5-nm bandwidth. The diffraction-limited output has a measured M2 value of 1.04 when the fiber is coiled to a diameter of 12 cm. The fiber amplifier slope efficiency is 70% with a polarization extinction ratio greater than 23 dB. It is shown how the phosphorus/aluminum ratio reduces photodarkening, and how a depressed-clad design improves higher-order mode filtering for reliable, efficient, and compact ytterbium-doped fiber amplifiers.

Paper Details

Date Published: 22 September 2010
PDF: 8 pages
Proc. SPIE 7750, Photonics North 2010, 775018 (22 September 2010); doi: 10.1117/12.872898
Show Author Affiliations
Mathieu Drolet, INO (Canada)
Pierre Laperle, INO (Canada)
Claude Paré, INO (Canada)
Huimin Zheng, INO (Canada)
Louis Desbiens, INO (Canada)
Antoine Proulx, INO (Canada)
Yves Taillon, INO (Canada)

Published in SPIE Proceedings Vol. 7750:
Photonics North 2010
Henry P. Schriemer; Rafael N. Kleiman, Editor(s)

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