Customized Itinerant Frequency Combs by Cascaded Nonlinear Effects.

Frequency combs are pivotal in nonlinear optics, with extensive applications in modern optics and precision measurement. Precise control over their critical parameters is essential to enhance performance and expand the range of applications. In this work, we develop a cascaded third-order nonlinear system to create an on-demand and customized itinerant frequency comb (IFC). Unlike traditional microcavity Kerr combs, the IFC decouples the comb center frequency from the cavity resonance, thereby enabling arbitrary spectral width scaling and flexible comb spacing adjustments. In particular, we demonstrate the real-time engineering of the central frequency of IFCs, thereby enabling the splicing and subdivision of frequency combs. These advances have the potential to enhance the performance of existing applications and expand new application scenarios by harnessing cascaded nonlinear effects.