Self-emergence of robust solitons in a microcavity

In many disciplines, states that emerge in open systems far from equilibrium are determined by a few global parameters^1,2. These states can often mimic thermodynamic equilibrium, a classic example being the oscillation threshold of a laser³ that resembles a phase transition in condensed matter. However, many classes of states cannot form spontaneously in dissipative systems, and this is the case for cavity solitons² that generally need to be induced by external perturbations, as in the case of optical memories^4,5. In the past decade, these highly localized states have enabled important advancements in microresonator-based optical frequency combs^6,7. However, the very advantages that make cavity solitons attractive for memories-their inability to form spontaneously from noise-have created fundamental challenges. As sources, microcombs require spontaneous and reliable initiation into a desired state that is intrinsically robust^8-20. Here we show that the slow non-linearities of a free-running microresonator-filtered fibre laser²¹ can transform temporal cavity solitons into the system's dominant attractor. This phenomenon leads to reliable self-starting oscillation of microcavity solitons that are naturally robust to perturbations, recovering spontaneously even after complete disruption. These emerge repeatably and controllably into a large region of the global system parameter space in which specific states, highly stable over long timeframes, can be achieved.