Highly efficient 1.064 µm upconversion pumped1.47 µm thuliumdoped fluoride fibre amplifier

A highly efficient amplifier has been demonstrated using the 1470 nm transition in a thulium doped fluoride fibre by upconversion pumping at 1064 nm. A small signal gain bandwidth of 35 nm was shown with a gain peak of around 19 dB occurring at 1462 nm. A maximum gain efficiency of 0.24 dB/mW, and output power of 17 dBm have been achieved, the latter for a launched pump power of 155 mW, indicating a power conversion efficiency of 34%.