Cat-and-mouse dynamics in faticons for fine-tuning comb line spacing

Faticons - vectorial localized structures in Kerr ring resonators - offer a powerful platform for linking nonlinear symmetry-breaking dynamics to frequency comb control. Arising from coupled polarization components, these states undergo spontaneous symmetry breaking (SSB), leading to intensity asymmetry and distinct propagation behaviors. Here, we identify a higher-order symmetry-breaking mechanism that produces a dynamic “cat-andmouse” interaction between the components, in which peak-power imbalance drives a continuous chasing effect and modifies the faticon’s propagation velocity. This velocity shift directly translates into changes in the roundtrip time and hence the repetition rate of the associated frequency comb, providing a route to fine-tuning comb line spacing. Furthermore, we show that an externally applied pump-intensity bias can replicate and extend this behaviour in a fully controlled and broadly accessible parameter regime, overcoming the limitations of intrinsic SSB. These results establish faticons as a flexible and robust mechanism for engineering soliton dynamics and tailoring frequency combs for applications in precision metrology, spectroscopy, and optical communications.