Backward pumping Tm-doped fiber amplifier with >60% slope efficiency

Abstract In this paper, an efficient all fiber Tm-doped fiber amplifier which is backward-pumped with multi-mode laser diodes at 793 nm is reported. A maximum slope efficiency of 64.4%, a maximum output power of 35.5 W, a spectral signal to noise ratio of 66 dB and an ideal Gaussian beam profile are achieved. The results indicate that the implementation of a backward pumping scheme and strong injection of the seed power can enhance the slope efficiency, which is particularly crucial for high power fiber amplifiers at 2 μ m.