Fig. 1. Er³⁺-, Ho³⁺-, and Dy³⁺-doped fluoride glasses.（a）Mid-infrared emission spectra^[19-22];（b）corresponding energy level diagrams, transitions, and pump methods^[19-29]

Fig. 2. Working mechanism of MSA effect

Fig. 3. SESAM mode-locked Ho³⁺/Pr³⁺ codoped ZBLAN fiber laser^[43].（a）Experimental setup;（b）time domain pulse sequence;（c）optical spectra in the CW and mode-locking regimes;（d）autocorrelation trace

Fig. 4. Commercial semiconductor materials or components mode-locked mid-infrared fluoride fiber lasers.（a）Experimental setup of the InAs mode-locked Ho³⁺/Pr³⁺ co-doped ZBLAN fiber ring oscillator at 2.86 μm and the autocorrelation trace^[47];（b）experimental setup of the SESAM mode-locked high-power Er³⁺-doped ZBLAN fiber laser at 2.78 μm and the output power evolution^[51];（c）experimental setup of the SESAM mode-locked tunable Er³⁺-doped ZBLAN fiber laser around 2.8 μm and the optical spectra^[57];（d）experimental setup of the SESAM mode-locked high-stability polarization-maintaining Er³⁺-doped ZBLAN fiber laser around 2.8 μm and the noise characteristics^[67]

Fig. 5. Device schematics and pulse trains of novel nanomaterials mode-locked ZBLAN fiber laser. (a) Black phosphorus mode-locked 2.77 μm all-fiber Er³⁺-doped ^[59]；(b) black phosphorus mode-locked 3.49 μm dual-wavelength pumped Er³⁺-doped^[58]; (c) gold nanowires mode-locked 2.86 μm Ho³⁺/Pr³⁺ co-doped^[65]

Fig. 6. Working mechanism of NPR effect

Fig. 7. NPR mode-locked Er³⁺-doped ZBLAN fluoride fiber ring oscillator at 2.8 μm ^[69]. (a) Schematic of setup; (b）optical spectra；（c）time domain pulse sequence;（d）autocorrelation trace

Fig. 8. Device schematic and correlated characteristic of NPR mode-locked mid-infrared fluoride fiber lasers. (a) NPR mode-locked 2.8 μm Er³⁺-doped ZBLAN fiber oscillator, amplifier, and compressor^[79];（b）NPR mode-locked tunable Er³⁺-doped ZBLAN fiber oscillator^[80];（c）NPR mode-locked dual-wavelength pumped Er³⁺-doped ZBLAN fiber oscillator^[81]

Fig. 9. Comparison of SA and FSF mode-locking mechanisms^[90]

Fig. 10. FSF mode-locked Dy³⁺-doped ZBLAN fiber laser based on AOTF^[90].（a）Experimental setup;（b）power evolution;（c） Q-switched and mode-locked optical spectra;（d）time domain pulse sequence;（e）autocorrelation trace;（f）tuned mode-locked spectra

Fig. 11. FSF mode-locked Dy³⁺-doped ZBLAN fiber laser based on AOM^[94].（a）Experimental setup;（b）optical spectrum

Table 1. Performance parameters of typical continuous wave（CW）mid-infrared Er³⁺, Ho³⁺, and Dy³⁺-doped fluoride fiber lasers

Table 2. Progress and performance parameters of MSA mode-locked mid-infrared fluoride fiber lasers

Table 3. Progress and performance parameters of NPR mode-locked mid-infrared fluoride fiber lasers

Table 4. Progress and performance parameters of FSF mode-locked mid-infrared fluoride fiber lasers