Nonreciprocal photonic topological order driven by uniform optical pumping

Photonic topological insulators (PTIs) have raised significant interest in recent years, in part because of their protected edge propagation. Most PTI realizations have been based on reciprocal platforms, with protection only from symmetry-preserving defects. Nonreciprocal PTIs protect against arbitrary disorder, but their implementation requires breaking reciprocity either through a magnetic bias or complex spatiotemporal modulation schemes. Here, we demonstrate that nonreciprocal topological protection can be achieved by optically pumping a nonlinear photonic crystal with a uniform bias field, drastically simplifying the implementation of quantum-Hall-like topological protection in silicon-compatible platforms for classical and quantum optics.