Dissipative soliton resonance in a normal dispersion all-polarization-maintaining thulium-doped fiber laser

• Demonstration of a new, PM fiber with an elliptical core and normal dispersion in the 2 µm spectral region. • A thulium-doped, mode-locked, all-PM fiber laser with net-normal dispersion was presented. • Investigation of dissipative soliton resonance (DSR) in the normal dispersion regime at the 2 µm wavelength. • Generation of linearly polarized optical pulses with duration tunable from ∼ 0.2 ns to 6 ns. We report a first demonstration of dissipative soliton resonance (DSR) in a normal dispersion thulium-doped fiber laser (TDFL) constructed entirely of polarization-maintaining fibers. A nonlinear fiber loop mirror with a combination of normal and anomalous dispersion fibers inside the loop ensures a self-starting mode-locking operation in the DSR regime. The oscillator generated linearly polarized optical pulses with a fundamental repetition frequency of 5.735 MHz and a nearly constant peak power clamped at ∼ 4.35 W. The pulse duration extends from 217 ps to 6 ns, when the pump power increases from 417 mW to 1.86 W. The maximum average output power of the DSR pulses was 151 mW, corresponding to the single pulse energy of 26 nJ.