Fig. 1. (a) Frequency-comb spectra in the absence (blue) and presence (red) of two-photon absorption. (b) The corresponding temporal evolution of (a) (blue curve). (c) The final stable flat top pulse in (b).

Fig. 2. (a) Spectra are generated in the presence of 3PA and FC effects (red), in the presence of 3PA without FC effects (blue), and in the absence of 3PA (green). (b) Temporal evolution of comb [blue curve in (a)] in the presence of 3PA without FC effects.

Fig. 3. (a) Spectra are generated in the presence of 4PA without FC effects (blue) and with FC effects (red). (b) Corresponding temporal profiles.

Fig. 4. (a) Spectra generated in the presence of 3PA and FC effects with different frequency separations of pumps. (b) Corresponding temporal evolution of blue curve in (a). (c) The final stable pulse of (b).

Fig. 5. (a) Spectrum generated in the presence of 4PA and FC effects. (b) Corresponding temporal evolution. (c) The final stable pulse of (b).

Fig. 6. (a)–(c) Spectra and (d)–(f) temporal profiles correspond to locations a, b, and c in temporal evolution of (g) with detuning of 0.05, 0.11, and 0.12, respectively.