Creating high-dimensional topological physics using a single ring resonator

In spaces of three or more dimensions, there exists topological physics of significant richness that has no lower-dimensional counterparts. To experimentally explore high-dimensional physics, it is advantageous to augment the physical space with synthetic dimensions. An emerging approach is to use a single modulated photonic ring resonator to form multiple synthetic frequency dimensions. However, all the high-dimensional Hamiltonians experimentally demonstrated in this approach are topologically trivial. Here we propose a general scheme to create high-dimensional topological physics using multiple synthetic frequency dimensions in a single ring resonator. This scheme utilizes specifically designed mode-selective modulations and mode conversions to create non-trivial topology. As examples, we numerically demonstrate a three-dimensional, two-band model exhibiting Weyl points and topological insulator phases, and a five-dimensional, four-band model exhibiting Yang monopoles and Weyl surfaces. Our results will facilitate the experimental studies and future applications of topological physics in high dimensions.