Fig. 1. Configuration of the "figure-9" mode-locked fiber laser

Fig. 2. Simulation results. (a) θ₁=45°, the transmission curves when tuning θ₂; (b) θ₂=135°, the transmission curves when tuning θ₁; (c) θ₂=135°, the transmission curves when tuning θ₁ slightly

Fig. 3. Physical diagram of 600 MHz Yb-doped fiber laser

Fig. 4. Pulse train (a) and spectrum (b) of Yb-doped fiber laser

Fig. 5. Autocorrelation trace of output pulses and Gauss fit

Fig. 6. Physical diagram of 280 MHz Er-doped fiber laser

Fig. 7. Pulse train (a) and spectrum (b) of Er-doped fiber laser

Fig. 8. Pulse autocorrelation trace under different fiber lengths. (a)-(b) The length of the collimator tail fiber is 62 cm; (c)-(d) Corresponds to 60 cm; (e)-(f) Corresponds to 58 cm; (g)-(h) Corresponds to 54 cm; (i)-(j) Corresponds to 50 cm

Fig. 9. (a) Autocorrelation trace of direct output pulses (black line) and Sech² fitting (red line); (b) Autocorrelation trace of compressed pulses (black line) and Sech² fitting (red line)

Fig. 10. Power stability of output laser. (a) Average power of the laser over 45 hours; (b) Output power versus pump power