Half-mJ All-Fiber-Based Single-Frequency Nanosecond Pulsed Fiber Laser at 2-μm

We report a high energy, high peak power, all-fiber-based single-frequency similar to 15-ns pulsed laser source at similar to 1918.4 nm in master oscillator-power amplifier configuration. The pulsed fiber laser seed was achieved by directly modulating a continuous-wave single-frequency fiber laser using an electro-optic modulator driven by an arbitrary waveform generator to pre-shape the pulses before amplification to mitigate pulse steepening and dynamic gain saturation. One piece of large (25-mu m) core, polarization-maintaining highly thulium-doped germanate glass fiber was used in the power amplifier stage to boost the energy and the peak power of the 15-ns pulses to >0.5 mJ and >33 kW without any nonlinearities.