Fig. 1. Time and frequency domain representations of microresonator-based optical frequency combs

Fig. 2. Dynamic evolution of soliton microcombs^［65］

Fig. 3. Soliton microcomb and corresponding generation methods

Fig. 4. Fabry-Perot resonator and its soliton microcomb spectrum^［85］

Fig. 5. Microbottle resonator and its Kerr frequency comb spectra^［34］

Fig. 6. Crystalline resonator and its dual-comb soliton spectrum^［115］

Fig. 7. Microsphere resonator and its dual-comb soliton spectra^［37］

Fig. 8. Microrod resonator and its soliton microcomb spectrum

Fig. 9. Microbubble resonator and its Kerr frequency comb spectra^［148］

Fig. 10. Applications of non-integrated microresonator-based optical frequency combs