Fig. 1. Schematic diagram of Ytterbium-doped fiber laser

Fig. 2. Schematic diagram of re-frequency locked feedback loop and frequency counting circuit

Fig. 3. (a) Diagram of fundamental frequency mode-locked pulse sequence spectrum; (b) Allen deviation analysis results of stabilized repetition rate

Fig. 4. Experimental results of the harmonic order varying with the pump power （In this experiment, when the pump power was higher than 650 mW, only coarse power increasement steps were carried out at high hamonic orders of mode-locking）

Fig. 5. Spectra under different harmonic mode-locked states

Fig. 6. (a) Fundamental frequency mode-locked pulse width; (b) 4th harmonic mode-locked pulse width

Fig. 7. [in Chinese]

Fig. 7. (a) The 3th harmonic mode-locked pulse spectrum; (b) The 7th harmonic mode-locked pulse spectrum; (c) The 15th harmonic mode-locked pulse spectrum; (d) The 20th harmonic mode-locked pulse spectrum

Fig. 8. (a) Allen deviation diagram of repetition frequency locking when the pump power is 575 mW; (b) Allen deviation diagram of repetition frequency locking when the pump power is 650 mW

Fig. 9. Phase noise of fundamental frequency mode locking and 3th harmonic mode locking and re-frequency locking