A Monolithic Thulium Doped Single Mode Fiber Laser with 1.5ns Pulsewidth and 8kW Peak Power

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 1.5 m 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.