Here we report a compact monolithic 2000nm pulsed laser with a single spatial mode output, ~1.5ns pulse duration, 8kW
peak power and >200mW average power at 20 kHz repetition rate. The gain-switched laser, consisting of a pair of fiber
Bragg gratings and 0.5m of thulium-doped single cladding fiber, was core pumped by a high peak power pulsed 1.5μm
laser. When the input pulse energy of the 20 kHz pump pulses was sufficient enough to saturate the Thulium doped fiber,
a stable 20 kHz pulse train was observed with measured linewidth of 0.05nm which corresponds to the limit of resolution
for the Optical Spectrum Analyzer. This compact, pulsed 2000 nm laser, to the authors' limited knowledge, represents
the first Tm-doped fiber laser with 8kW peak power and several ns pulse duration; which is less than the previously
reported tens of ns pulsewidth previously reported from gain-switched Tm-doped fiber lasers.
We report on the pulse shape of an actively Q-switched fiber laser. This master oscillator power amplifier architecture
generates pulses with multiple peaks due to its intrinsic dynamics. Modeling and experimental results provide us a
detailed understanding of the relative importance of the different time constants on the dynamics of the laser, which
allows us to define optimized design parameters that lead to smooth and controlled pulse shapes. This solution is simple
and robust; operation over a broad range of repetition rate and output power is achieved without any adjustment of the
laser settings, and the corresponding variation of the optical performances is minimal.