High power tandem-pumped thulium-doped fiber laser

We propose a cascaded tandem pumping technique and show its high power and high efficient operation in the 2-mu m wavelength region, opening up a new way to scale the output power of the 2-mu m fiber laser to new levels (e. g. 10 kW). Using a 1942 nm Tm3+ fiber laser as the pump source with the co-(counter-) propagating configuration, the 2020 nm Tm3+ fiber laser generates 34.68 W (35.15W) of output power with 84.4% (86.3%) optical-to-optical efficiency and 91.7% (92.4%) slope efficiency, with respect to launched pump power. It provides the highest slope efficiency reported for 2-mu m Tm3+-doped fiber lasers, and the highest output power for all-fiber tandem-pumped 2-mu m fiber oscillators. This system fulfills the complete structure of the proposed cascaded tandem pumping technique in the 2-mu m wavelength region (similar to 1900 nm -> similar to 1940 nm -> similar to 2020 nm). Numerical analysis is also carried out to show the power scaling capability and efficiency of the cascaded tandem pumping technique. (C) 2015 Optical Society of America