Non-Hermitian control of topological light

We present non-Hermitian control of topological light, enabling dynamic manipulation of both light propagation and coupling in topological photonic systems. By spatially modulating gain and loss, we engineer reconfigurable non-Hermitian domain walls that steer topological edge states along arbitrary trajectories, enabling robust, disorder-immune light routing within the bulk of a photonic topological insulator, without altering its physical structure. In parallel, we introduce a pseudo-spin-flip coupling scheme between identical topological domains. This generates hybridized co-propagating interface states whose interference enables programmable directional coupling. By tuning the gain-loss distribution, we dynamically switch between “cross” and “bar” coupling states and continuously control the power splitting ratio, realizing a compact, topologically protected directional coupler. Our demonstrated non-Hermitian control of topological light unlocks reconfigurable, fault-tolerant light transport in topological photonic circuits for scalable, dynamic light routing and on-chip optical signal processing.