posted on 2023-02-13, 14:31authored byMartin Richardson, Justin Cook, Alex Sincore, Nicholas Vail, Ria G. Krämer, Thorsten A. Goebel, Patrick Roumayah, Joshua Bryan, Nathan Bodnar, Stefan Nolte
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.
History
Funder Name
Air Force Office of Scientific Research; Bundesministerium für Wirtschaft und Energie; AFOSR (FA9550-19-1-0127)