Fundamental and Third Harmonic Mode Coupling Induced Single Soliton Generation in Kerr Microresonators

The single soliton propagating in a microresonator (MRR) is characterized by a smooth spectrum. However, the number of solitons that propagate in an MRR in the anomalous dispersion regime is usually stochastic and gives rise to a complex spectrum. In this paper, we introduce a new passive mechanism based on third-harmonic-induced nonlinear coupling for the formation of a single deterministic soliton in an MRR. We show that with appropriate fundamental and third harmonic mode coupling strength and a slight phase mismatch, deterministic single soliton generation can be realized by simply scanning the detuning of a continuous wave serving as a pump. Under strong mode coupling strength, a relatively smaller wave vector mismatch within suitable range can be used for single soliton generation. Our work provides a potential approach for on-chip generation of coherent optical Kerr combs and efficient THG conversion.