Dynamically reconfigurable topological routing in nonlinear photonic systems

One of the defining features of photonic topological materials is the guaranteed existence of boundary-localized states at the interfaces between topologically distinct regions. In particular, the robustness of these states against fabrication imperfections and other defects enables a new dimension of control over the flow of light and has been utilized in plethora photonic devices, such as lasers and routers. However, as the propagation path of any such protected state is bound to the interface between regions with different topology, the functionality of photonic devices leveraging these states is fixed during fabrication. Here, we propose a mechanism for dynamic control over a driven dissipative system's local topology, yielding reconfigurable topological interfaces and thus tunable paths for protected routing. We illustrate our approach in non-resonantly pumped polariton lattices, where the nonlinear interaction between the polaritons and the exciton reservoir due to non-resonant pumping can yield a dynamical change of the topology. Moreover, using a continuous model of the polariton system based on a driven-dissipative Gross-Pitaevskii equation alongside the spectral localizer framework, we show that the local changes in the nonlinear non-Hermitian system's topology are captured by a local Chern marker. Looking forward, we anticipate such reconfigurable topological routing will enable the realization of novel classes of topological photonic devices.