Multi-colour frequency combs in the Kerr microresonators

This work presents multi-colour frequency comb generation in integrated silicon nitride ($\mathrm{Si}_{3} \mathrm{~N}_{4}$) microresonators via various four-wave mixing processes. Through careful engineering of dispersion and coupling rates, our resonator effectively induces optical parametric oscillation before the conventional Kerr comb generation, yielding signal and idler sidebands located far from the pump light frequency. By further increasing the pump power, multiple frequency combs centered on the signal, pump, and idler frequencies emerge due to their interactions with Kerr nonlinear effects. Our findings demonstrate even using a single pump, one can achieve multi-combs with diverse center frequencies and repetition rates within a single $\mathrm{Si}_{3} \mathrm{~N}_{4}$ resonator. These results contribute to advancing nonlinear dynamic research within integrated photonic platforms and offer new opportunities for integrated frequency combs in spectroscopy and sensing applications.