A frequency-encoded photonic Chern insulator

Chern insulators are topological phases of matter with broken time-reversal symmetry. Albeit their technological interest, these phases have proven to be highly challenging to implement in photonics systems, notably due to the typically low magneto-optical response of matter at optical or near-infrared frequencies. In this presentation, I will describe an experimental work in which we realize a photonic Chern insulator, inspired from the Haldane model, using the synthetic frequency dimension of a time-modulated optical fibre loop platform. Thanks to the remarkable tunability and driven-dissipative nature of our system, we demonstrate a thorough characterization of the resulting bands’ topology. This includes band structure measurements in all regions of the topological phase diagram, extraction of the Berry curvature across the entire Brillouin zone and of the resulting Chern number associated to each band, and observation of a photonic analogue of the quantized transverse Hall conductivity. Our work paves the way to engineering backscattering-immune flow of light in frequency-multiplexed photonic systems.