Fig. 1. Classification diagram of saturable absorbers

Fig. 2. Mechanism of NPE saturable absorption effect^[26]

Fig. 3. All-polarization-maintaining fiber NPE mode-locking fiber laser setup and the mechanism of saturable absorption effect^[24]

Fig. 4. Experimental setup of intelligence NPE mode-locking fiber laser^[30]

Fig. 5. Mechanism of NOLM saturable absorption effect^[38]

Fig. 6. Experimental setup of all-polarization-maintaining figure 8 mode-locking fiber laser^[32]

Fig. 7. Experimental setup of high-repetition figure 9 mode-locking fiber laser^[34]

Fig. 8. Experimental setup of the visible-wavelength NOLM mode-locked fiber laser^[58]. (a) Schematic; (b) photograph of 635 nm all-beam structure figure 8 DSR fiber laser

Fig. 9. Schematic diagram of saturable absorption effect of nanomaterials^[13]

Fig. 10. Novel nano-materials saturable absorbers^[69]

Fig. 11. Schematic and image of gate-controlled all-fiber graphene devices^[78]

Fig. 12. Schematic diagram of NLMMI saturable absorption^[80]

Fig. 13. SMF-SIMF-GIMF-SMF nonlinear multimode interference Tm-doped fiber laser^[80]

Fig. 14. NCF-GIMF NLMMI nonlinear multimode interference fiber laser^[82]

Fig. 15. Schematic diagram of Mamyshev regenerator saturable absorption effect^[3]

Fig. 16. Schematic diagram of the ring Mamyshev oscillator^[24]

Fig. 17. Numerical simulation results for 190 nJ output pulse^[24]. (a) Spectral evolution of the pulse in the cavity; (b) evolution of the pulse duration (circles) and RMS bandwidth (squares)