DOI: 10.1364/oe.487601 ISSN: 1094-4087

100 W, tunable in-band thulium fiber amplifier pumped by incoherently combined 1.9 µm fiber lasers

Justin Cook, Alex Sincore, Nicholas Vail, Ria G. Krämer, Thorsten A. Goebel, Patrick Roumayah, Joshua Bryan, Nathan Bodnar, Stefan Nolte, Martin Richardson
  • Atomic and Molecular Physics, and Optics

We detail the design and performance of a high efficiency in-band pumped thulium fiber amplifier operating at the 100 W level. Using a novel pumping architecture based on three incoherently combined thulium fiber oscillators at 1904 nm and a seed laser tunable from 1970–1990 nm, efficient amplification is demonstrated in a high dopant concentration 25/65/250 µm thulium fiber. Here we use the 65 µm pedestal surrounding the core as a pump cladding to increase the cladding to core overlap and improve the overall pump absorption. Up to 89% slope efficiency is obtained with ∼100 W output power at 1990 nm. These results indicate that in-band pumping is a viable route to circumvent the thermal limitations associated with 793 nm diode pumping and provide a pathway for development of multi-kW laser sources in the 2 µm spectral window.

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