On-chip multi-timescale spatiotemporal optical synchronization.

Mode locking is foundational to nonlinear optics, enabling advances in metrology, spectroscopy, and communications. However, it remains unexplored in nonharmonic, multi-timescale regimes. Here, we realize on-chip multi-timescale synchronization using topological photonics. We design a two-dimensional lattice of 261 coupled silicon nitride ring resonators that supports nested mode-locked states with fast ( [Formula: see text] 1 terahertz) single-ring and slow ( [Formula: see text] 3 gigahertz) topological super-ring timescales. We observe clear signatures of multi-timescale mode locking, including a quadratic distribution of pump noise across both azimuthal mode families, consistent with theory. These findings are supported by near-transform-limited repetition beats and the emergence of periodic temporal patterns on the slow timescale. The edge-confined states show distinct dynamics from bulk and single-ring modes, enabling clear identification. Our results establish topological frequency combs as a robust platform for independently tunable, lattice-scale synchronization, opening new directions for exploring the interplay of nonlinearity and topology in integrated photonics.