Fig. 1. Experimental setup

Fig. 2. Output characteristics of experimental setup. (a) Optical spectrum (inset: optical spectrum in the range of 925‒1100 nm); (b) frequency spectrum; (c) pulse sequence diagram displayed on the oscilloscope under single-pulse mode-locking state; (d) waveform diagram of a single pulse displayed under single-pulse mode-locking state

Fig. 3. Process diagram of establishing a stable single-pulse mode-locking state. (a) Two-dimensional time-domain graph directly detected by the oscilloscope; (b) two-dimensional time-domain graph of Fig. 3(a) from the 1400th to the 1700th cycle; (c) three-dimensional time-domain graph directly detected by the oscilloscope; (d) three-dimensional time-domain graph of Fig. 3(c) from the 0th to the 1500th cycle; (e) two-dimensional time-domain graph of Fig. 3(a) from the 0th to the 1500th cycle

Fig. 4. Process diagram of establishing a stable double-pulse mode-locking state. (a) Two-dimensional time-domain graph directly detected by the oscilloscope; (b) two-dimensional time-domain graph of Fig. 4(a) from the 1200th to the 1600th cycle; (c) two-dimensional time-domain graph of Fig. 4(a) from the 1900th to the 2200th cycle; (d) three-dimensional time-domain graph directly detected by the oscilloscope; (e) three-dimensional time-domain graph of Fig. 4(d) from the 0th to the 1200th cycle; (f) two-dimensional time-domain graph of Fig. 4(a) from the 0th to the 1500th cycle

Fig. 5. Process diagram of establishing a stable triple-pulse mode-locking state. (a) Two-dimensional time-domain graph directly detected by the oscilloscope; (b) two-dimensional time-domain graph of Fig. 5(a) from the 1400th to the 1650th cycle; (c) two-dimensional time-domain graph of Fig. 5(a) from the 1850th to the 2050th cycle; (d) three-dimensional time-domain graph directly detected by the oscilloscope; (e) three-dimensional time-domain graph of Fig. 5(d) from the 0th to the 1500th cycle; (f) two-dimensional time-domain graph of Fig. 5(a) from the 0th to the 1500th cycle