1.35 μJ, 5.33 W noise-like pulse emission from an all-polarization maintaining holmium-doped fiber laser system

We present a 2.1 μm noise-like pulse generation from an all-polarization maintaining (PM) holmium-doped fiber laser system containing seed laser and amplifier, for the first time. The seed relies on nonlinear amplifying loop mirror mechanism for achieving mode-locking. The cavity length and splitting ratio of optical coupler are considered to be optimized to obtain high energy noise-like pulse (NLP). Thanks to the all-PM scheme, the seed laser is capable of self-starting operation, driving a 2106.9 nm, 0.409 W NLP train with pulse energy of 103.5 nJ and envelope width of 2.41 ns. To further enhance the power of the pulsed seed laser, a bi-directional pumping amplifier is designed, which is able to scale the power of NLP to 5.33 W. The corresponding pulse energy reaches 1.35 μJ. The spectral tail has slight broadening as well as the pulse maintains a rectangular shape. The relative standard deviation of the laser power in one hour is 0.2%, indicating the stable operation capability of the laser system. Such 2.1 μm all-PM NLP laser system could be a useful pump source in industrial processing and supercontinuum generation.