Fig. 3: Formation process of microcombs.
a Four representative optical spectra of microcombs. The amplitude of cavity-laser detuning is gradually decreased from top to bottom. The second and third harmonic generation is observed first, followed by the primary combs in all three frequency bands. Subcombs are then generated and they slowly merge with the decrease of detuning. b Simulated microcomb formation process. Pump detuning is scanned from shorter to longer wavelength, and the spectrum evolution of microcomb is presented. The intracavity power for three bands is normalized to the largest value of their own bands.
