Gain-switched, Yb-doped, all-fiber laser with narrow bandwidth

Rare-earth doped fiber lasers have emerged as attractive alternatives to traditional lasers in material processing due to the ruggedness, high efficiencies, and excellent beam quality [1]. The development of pulsed fiber lasers is driven by the fact that specific applications require different peak powers, repetition rates, and pulse energies. Some of the methods of pulsing the lasers completely avoid free-space coupled components and they benefit greatly from the all-fiber robustness. Examples of all-fiber pulsed laser technologies are mode-locking by nonlinear polarization rotation and Q-switching by using custom-made saturable absorber fiber [2]. Gain-switching of a fiber laser is a less-investigated method that makes use of the inherent relaxation oscillations of the fiber laser by fast modulation of the pump [3,4]. The advantage is that only readily available components for a CW laser are required. Gain-switched fiber lasers can deliver high pulse energies and has applications in e.g. supercontinuum generation [4], where the increased peak power reduces the dependence on the zero dispersion wavelength [5].