Quadratic bright and dark solitons in on-chip degenerate optical parametric oscillators

Temporal Kerr cavity solitons in passive optical resonators have attracted significant attention over the last decade. After being demonstrated on several platforms, hybrid Kerr architectures have appeared to increase conversion efficiency or energy extraction. Another approach is to rely on second-order nonlinearity to generate solitons. Such quadratic cavity solitons offer two main advantages over their Kerr counterparts: reduced pump powers and frequency combs formation far away from the pump frequency. In my talk, I will present our recent investigations of two types of quadratic solitons in an on-chip degenerate optical parametric oscillator, leveraging the recent advances in lithium niobate nanophotonic. The first one is the topological soliton, arising from the locking between domain walls. The second one is a sech-squared cavity soliton, found when a slight phase mismatch is introduced. These results constitute a first step towards broadband frequency combs in quadratic resonators with low finesse and normal dispersion.