# Dynamically reconfigurable topological routing in nonlinear photonic systems

## TL;DR

Researchers developed a way to dynamically control the routing of light in photonic systems using nonlinear interactions, enabling ultrafast and reconfigurable topological interfaces.

## Contribution

A novel mechanism for dynamically reconfiguring topological interfaces in nonlinear photonic systems is introduced, enabling tunable and ultrafast routing of topologically protected states.

## Key findings

- Nonlinear interactions in polariton lattices allow picosecond-scale changes in chiral edge state propagation paths.
- A generalized spectral localizer framework confirms topological dynamics in non-linear non-Hermitian Chern materials.
- Local changes in polariton lattice topology are captured by a local Chern marker.

## Abstract

The propagation path of topologically protected states is bound to the interface between regions with different topology, and as such, the functionality of linear 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 picosecond-scale changes in the propagation paths of the chiral edge states. To analytically confirm the numerically observed topological dynamics, we generalize the spectral localizer framework to non-linear non-Hermitian Chern materials and apply this framework to a continuous model of the polariton system based on a driven-dissipative Gross-Pitaevskii equation. In doing so, we show that the local changes in the polariton lattice’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.

Dynamic reconfiguration of photonic topological interfaces enables ultrafast routing at telecommunications wavelengths by leveraging nonlinear exciton–polariton interactions.