Fig. 1. (a) Schematic diagram of the experimental setup. Red arrow represents the direction of laser transmission, and the small diagram shows the SA structure; (b) transmission spectrum of the NCF-GIMF device; (c) nonlinear saturable absorption curve of the NCF-GIMF device.

Fig. 2. Conventional mode-locked single soliton outputs. (a) Optical spectrum; (b) autocorrelation trace; (c) pulse train; (d) RF spectrum.

Fig. 3. Output of stable tight soliton pairs. (a) Optical spectrum; (b) autocorrelation trace; (c) pulse train; (d) RF spectrum.

Fig. 4. Tunable wavelength spectra in tight soliton pairs.

Fig. 5. Relationship between the stretched length of the SA and wavelength.

Fig. 6. Autocorrelation traces with different spectral modulation periods. The profiles in red are optical spectra with details in enlarged scale in the corner. The profiles in blue are autocorrelation traces with pulse width in the corner, corresponding to the panels on the left.

Fig. 7. (a)–(c) Different spectra of quasi-bound pairs; (d)–(f) corresponding autocorrelation traces.