Determining the relative impact of quantum efficiency and core propagation loss on efficient power scaling of thulium-doped silica fibre lasers

Buckthorpe, Martin Paul, Švejkar, Richard and Clarkson, Andy (2024) Determining the relative impact of quantum efficiency and core propagation loss on efficient power scaling of thulium-doped silica fibre lasers. In Solid State Lasers XXXIII: Technology and Devices. vol. 12864, SPIE. 7 pp . (doi:10.1117/12.3002641).

Abstract

A method for determining the quantum efficiency and core propagation loss in thulium-doped silica fibres is presented. The results provide evidence that thermal management of the fibre is a critical experimental parameter for achieving accurate predictions of the quantum efficiency and core propagation loss of the fibre with this method. By submerging a thulium-doped silica fibre with a ‘nested-ring’ structured core profile in a temperature-controlled water bath, a quantum efficiency of 1.93 was measured, providing evidence that the high doping level (4 wt. %) is successfully promoting the ‘two-for-one’ cross-relaxation process. Measurements of a ‘conventional’ thulium fibre with a uniformly doped core at a concentration of 2 wt. % gave a quantum efficiency of 1.65, providing further evidence of the relationship betweenincreasing doping concentration and increasing rate of ‘two-for-one’ cross-relaxation. Measurements of core propagation loss gave ~0.15 dB/m for both fibres, which is suggestive that core propagation loss presents a major issue for efficient power scaling to the kilowatt regime

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Contributors

Author: Martin Paul Buckthorpe

Author: Richard Švejkar

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