Spatial mode-interaction induced single soliton generation in microresonators

Soliton mode-locking in microresonators enables chip-scale coherent optical frequency comb generation. However, it usually leads to multi-soliton combs with structured spectrum. Instead, the smooth spectrum of single soliton is favored for applications. Here, we introduce, experimentally and numerically, a passive mechanism for single temporal soliton formation arising from spatial mode-interaction in microresonators. Deterministic single soliton generation is observed for microresonators with strong mode-interaction in experiments and simulations. Further simulations demonstrate that the soliton number is reduced to one in order to lower the nonlinear loss into mode-interaction induced Cherenkov radiation (CR). Our results give important insights into soliton-CR interaction in cavities.