In this Letter, we present a figure-eight all-PM-fiber laser oscillator design with a nonlinear optical loop mirror as an artificial saturable absorber. Unlike previous constructions using the same mode-locking technique, our cavity is constructed entirely of polarization-maintaining (PM) fibers, making the oscillator more resistant to thermal and mechanical perturbations. Two simple and robust laser configurations that differ by the output coupling ratio (70% or 30%) are presented. The first configuration delivers high energy pulses of 3.5 nJ, and the second configuration delivers pulses of 1.6 nJ at a common repetition rate of 15 MHz. In either configuration, the pulsed operation is stable, and the laser operates in a single pulse train regime, even for pump powers approaching twice the power required for mode-locking. We have also observed that, at higher intracavity powers, stimulated Raman scattering plays a significant role.

We demonstrate a novel method of mid-infrared (mid-IR) supercontinuum (SC) generation with the use of a 2 µm gain-switched self-mode-locked thulium-doped fiber laser. SC radiation ranging from ~1.9 to 3.8 µm wavelength, generated in a single-mode ZBLAN fiber with a zero-dispersion wavelength (ZDW) shifted to ~1.9 µm, is reported. An average output power of 0.74 W with 0.27 W at wavelengths longer than 2.4 µm was measured. It is, to the best of our knowledge, the first report on such an approach to generate a mid-IR SC in optical fibers.

We report high-power supercontinuum (SC) generation in a step-index fluorozirconate (ZBLAN) fiber with a zero-dispersion wavelength shifted to $\sim 1.9\mathrm{\mu m}$. Pumping the fluoride fiber with 2.75 W of power provided by a thulium-doped fiber amplifier, a continuous spectrum extending from $\sim 0.85$ to 4.2 μm with 2.24 W of average output power was achieved. Over 61% (1.37 W) of the total output power corresponds to wavelengths longer than 3 μm, which shows, to the best of our knowledge, the highest power conversion efficiency toward the mid-IR spectral band in relation to the output spectrum width. A linear SC power scalability up to 5.24 W, with a spectral band of $\sim 0.9–4\mathrm{\mu m}$, with repetition rate and pump power provided by a 1.55 μm fiber master-oscillator power amplifier system, is also demonstrated.

We investigate noise-like pulse (NLP) generation in a mode-locked thulium-doped fiber laser with nonlinear amplifying loop mirror (NALM) and different net anomalous dispersions. The all-polarization maintaining (PM) fiber oscillator generates pulse trains with a frequency adjustable in the range of 4.06–20.4 MHz by utilizing different lengths of PM passive fiber in the NALM loop. An NLP with a coherence spike width of 232 fs was generated at 1993.6 nm with a 3-dB spectral width of 32.6 nm when the net cavity dispersion was −0.711 $\text{ps}^2$ .

Broadband, mid-infrared supercontinuum generation in a step-index fluoroindate fibre is reported. By using ~70-picosecond laser pulses at 2.02 μm, provided by an optical parametric generator, a wide spectrum with a cut-off wavelength at 5.25 μm and a 5-dB bandwidth covering the entire 2–5 μm spectral interval has been demonstrated for the first time. The behaviour of the supercontinuum was investigated by changing the peak power and the wavelength of the pump pulses. This allowed the optimal pumping conditions to be determined for the nonlinear medium that was used. The optical damage threshold for the fluoroindate fibre was experimentally found to be ~200 GW/cm².