Fig. 1. (a) Schematic of Yb-doped fiber laser mode locked by NPR, (b) comb transmission spectra induced by NPR

Fig. 2. Switchable mode-locking at 1 042.8 nm and 1 050.2 nm. (a), (b) Mode-locking spectrum; (c), (d) Pulse train; (e), (f) Single pulse; (g), (h) RF spectrum

Fig. 3. Switchable mode-locked spectra at 1 040.9 nm and 1 048.1 nm

Fig. 4. Tunable wavelength from 1 042.72 nm to 1 045.34 nm under pump power of 395 mW

Fig. 5. Dual-wavelength mode locking. (a) Dual-wavelength spectrum; (b) Pulse train

Fig. 6. Harmonic mode-locking. （a） Optical spectrum; (b) Pulse train; (c) RF spectrum