Gaida, C.C.GaidaKienel, M.M.KienelMueller, M.M.MuellerKlenke, A.A.KlenkeGebhardt, M.M.GebhardtStutzki, F.F.StutzkiJauregui, C.C.JaureguiLimpert, JensJensLimpertTünnermann, AndreasAndreasTünnermann2022-03-052022-03-052015https://publica.fraunhofer.de/handle/publica/24097410.1364/OL.40.002301The efficient coherent combination of two ultrafast Tm-doped fiber amplifiers in the 2-mu m wavelength region is demonstrated. The performance of the combined amplifiers is compared to the output characteristics of a single amplifier being limited by the onset of detrimental nonlinear effects. Nearly transform-limited pulses with 830-fs duration, 22-mu J pulse energy, and 25-MW peak power have been achieved with a combining efficiency greater than 90%. Based on this result, it can be expected that 2-mu m-ultrafast-fiber-laser systems will enter new performance realms in the near future.en535journal article