Fig. 1. (a) SEM photograph of the TI Bi2Te3 nanosheets; (b) microscope photo of the TI-based SA; (c) photo of the TI-based SA via visible light; (d) time-dependent depositing process; (e) nonlinear SA curve.

Fig. 2. Experimental setup of the passively mode-locked THDFL.

Fig. 3. Characteristics of fundamental mode-locked solitons; (a) optical spectrum; (b) pulse train; (c) RF spectrum, RBW=1  kHz. Inset, span from 0 to 500 MHz; (d) autocorrelation trace at an amplified average power of ∼60  mW. Inset, corresponding spectrum.

Fig. 4. Temporal characteristics of mode-locked THDFL with bunched soliton numbers as follows in a single bunch; (a) 2; (b) 4; (c) 10; (d) 15.

Fig. 5. Characteristics of soliton bunches; (a) hysteresis phenomenon of the bunched soliton number versus the pump power; (b) output spectra.

Fig. 6. Characteristics of harmonically mode-locked solitons; (a) soliton train for the fifth harmonic order; (b) soliton train for the 10th harmonic order; (c) evolutions of the output power and harmonic orders versus the pump power; (d) output spectra.