Fig. 1. (a) Experimental setup of a mid-infrared dual-comb system based on a single-cavity dual-wavelength mode-locked laser (MLL); (b) Dual-comb repetition rate difference locking scheme with common hydrogen clock reference

Fig. 2. The output characteristics of dual-comb light source. The output optical spectrums of (a) oscillator and (b) amplifier; (c)-(d) The auto-correlation traces of comb1 and comb2 after amplification and compression; (e)-(f) The radio spectra of dual-comb at different repetition rate difference

Fig. 3. (a)-(b) Temporal drifts of repetition rates of the bidirectional pulses; (c)-(d) Comparison of ∆f_r drifts with and without phase-locking

Fig. 4. (a) Multiperiod time domain interferogram; (b) The radio frequency domain multi-heterodyne beat notes

Fig. 5. (a)-(b) The mid-infrared optical spectrums of two combs after Si₃N₄ waveguide