Gain-Switched 2-μm Fiber Laser System Providing Kilowatt Peak-Power Mode-Locked Resembling Pulses and Its Application to Supercontinuum Generation in Fluoride Fibers

A fast gain-switched Tm-doped fiber laser and amplifier system providing stable 17-ns pulses with a 0.64-mJ energy and 35.6-kW peak power at 25 kHz is demonstrated. Then, self-starting mode-locked resembling pulses with duration of <;200 ps, recorded within the gain-switched pulse envelope, were achieved in the same laser cavity. By amplifying the pulse train in a Tm-doped fiber amplifier, an average output power of 6.8 W at a ~15-ns full width at half maximum gain-switch envelope and a ~36.9-μJ subpulse with a peak power of up to 115.6 kW were demonstrated. To the best of our knowledge, this is the shortest gain-switched and mode-locked-like pulse as well as the highest peak-power that has been demonstrated in this type of laser system. A mid-infrared supercontinuum generation with a total output power of 2.45 W and a cutoff wavelength at 4.4 μm is also reported.