Black phosphorus (BP) as a novel class of two-dimension (2D) materials has recently attracted enormous attention as a result of its unique physical and chemical features. The remarkably strong light-matter interaction and tunable direct band-gap at a wide range make it an ideal candidate especially in the mid-infrared wavelength region as the saturable absorber (SA). In this paper, the simple and effective liquid phase exfoliation (LPE) method was used to fabricate BP. By introducing the same BP SA into two specifically designed rare earth ions doped fluoride fiber lasers at mid-infrared wavebands, Q-switching with the pulse energy of 4.93 μJ and mode-locking with the pulse duration of 8.6 ps were obtained, respectively. The operation wavelength of ~2970 nm for generated pulse is the reported longest wavelength for BP SA based fiber lasers.

We demonstrate a self-starting dual-wavelength mode-locked fiber laser at a 2 μm spectral region by using a fiber taper in a Tm³⁺-doped ring fiber cavity. The fiber taper fabricated with a flame brushing technique was used as a periodic filter with a modulation depth of ~3.61 dB and a modulation period of ~7.3 nm, respectively. Diverse dual-wavelength regimes including continuous wave (CW)/multi-soliton, soliton/multi-soliton, and soliton/soliton regimes were obtained by adjusting pump power. Wavelength tuning for the dual-wavelength was also precisely controllable through stretching the fiber taper carefully. The tuning range was ~7 nm which was limited by the modulation period of the taper. By inserting a 10.0 m dispersion compensation fiber (DCF) into the fiber cavity, a stable dual-wavelength dissipative-soliton operation was obtained at 2 μm spectral region for the first time.

We report a tunable passively Q-switched Ho(3+)-doped ZBLAN fiber laser at 3 μm waveband using a Fe(2+):ZnSe crystal as saturable absorber (SA) and a plane ruled grating in Littrow configuration as wavelength tuning element. Stable pulse trains with ~85 nm tuning range from 2919.1 nm to 3004.2 nm and spectrum bandwidths of ~1 nm were achieved for the Fe(2+):ZnSe crystal with an initial transmission (IT) of 69%. Pulse duration increased from 1.23 μs to 2.35 μs and repetition rate decreased from 96.1 kHz to 43.56 kHz with the extension towards long wavelength direction. With the IT increasing to 79% and then 89%, though the available tuning range was slightly shortened, higher output power, pulse energy and slope efficiency were obtained with the slightly increased pulse duration and repetition rate. Maximum output power of 337 mW at a slope efficiency of 11.44% and pulse energy of 5.64 μJ were achieved at ~2970 nm and ~2991 nm, respectively. High signal noise ratio (SNR) of over 50 dB across the whole tuning range for the three ITs Fe(2+):ZnSe crystals indicated the stable Q-switching. To our knowledge, this is the first reported wavelength tunable passively Q-switched ZBLAN fiber laser.

We reported a high average power and energy microsecond pulse erbium-doped fluoride fiber MOPA system centered at 2786.8 nm. The master oscillator was a passively Q-switched erbium-doped fluoride fiber laser based on SESAM in a linear cavity. Then a one-stage erbium-doped fluoride fiber amplifier was used to boost its average output power to 4.2 W and pulse energy to 58.87 μJ. The pulse duration and repetition rate were 2.29 µs and 71.73 kHz, respectively. To the best of our knowledge, the achieved average output power and pulse energy are the recorded levels for the passively Q-switched fiber lasers at 3 μm wavelength region.

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