High pulse energy sub-nanosecond Tm-doped fiber laser

We report a core pumped thulium-doped fiber amplifier that generates 1.4 mu J pulses at 1980 nm with a repetition rate of 3.6 MHz preserving the original spectral bandwidth of the oscillator. The amplifier chain is seeded by a passively mode-locked fiber laser with 5 mW output power and the pulses are stretched to 800 picoseconds. The amplifier is core pumped by a single mode erbium fiber laser. The slope efficiency is 35%. To the best of our knowledge, this is the first demonstration of sub nanosecond pulses with energies higher than 1 mu J coming out of a thulium-doped fiber amplifier.