Gain-switched thulium-doped fiber laser with ultra-wide tuning range

We demonstrate an all-fiber gain-switched thulium-doped fiber laser (TDFL) producing nanosecond pulses with variable wavelength in the 2 mu m waveband. The laser features tunable operation in an ultra-wide spectral region of 1765-2055 nm (24 THz). The nearly 300 nm tunability doubles the record tuning range of existing gain-switched fiber lasers, and to the best of our knowledge, presents the broadest tuning range that has been reported for a monolithic pulsed rare earth doped fiber laser to date. The TDFL can operate at a repetition rate of 5 -100 kHz with a pulse width as short as similar to 200 ns. A modest compromise in the tuning range allows pulse width reduction to sub-100 ns.