Laser cavity-soliton microcombs

Microcavity-based frequency combs, or 'microcombs'(1,2), have enabled many fundamental breakthroughs(3-21) through the discovery of temporal cavity-solitons. These self-localized waves, described by the Lugiato-Lefever equation(22), are sustained by a background of radiation usually containing 95% of the total power(23). Simple methods for their efficient generation and control are currently being investigated to finally establish microcombs as out-of-the-lab tools(24). Here, we demonstrate microcomb laser cavity-solitons. Laser cavity-solitons are intrinsically background-free and have underpinned key breakthroughs in semiconductor lasers(22,25-28). By merging their properties with the physics of multimode systems(29), we provide a new paradigm for soliton generation and control in microcavities. We demonstrate 50-nm-wide bright soliton combs induced at average powers more than one order of magnitude lower than the Lugiato-Lefever soliton power threshold(22), measuring a mode efficiency of 75% versus the theoretical limit of 5% for bright Lugiato-Lefever solitons(23). Finally, we can tune the repetition rate by well over a megahertz without any active feedback.