Theoretical Analysis of Microcavity Simultons Reinforced by (2) and (3) Nonlinearities

High -Q microcavities with quadratic and cubic nonlinearities add lots of versatility in controlling microcombs. Here, we study microcavity simulton and soliton dynamics reinforced by both chi(2) and chi(3) nonlinearities in a continuously pumped microcavity. Theoretical analysis based on the Lagrangian approach reveals the soliton peak power and gain -loss balance are impacted by the flat part of the intracavity pump, while the dark -pulse part of the pump leads to a nearly constant soliton group velocity change. We also derived a soliton conversion efficiency upper limit that is fully determined by the coupling condition and the quantum -limited soliton timing jitter in the chi(2;3) system. Numerical simulations confirm the analytical results. Our theory is particularly useful for investigating AlN microcombs and sheds light on the interplay between chi(2) and chi(3) nonlinearities within microcavity simultons.