# Lasing in topological edge states of a one-dimensional lattice

## Abstract

Topology describes properties that remain unaffected by smooth distortions. Its main hallmark is the emergence of edge states localized at the boundary between regions characterized by distinct topological invariants. Because their properties are inherited from the topology of the bulk, these edge states present a strong immunity to distortions of the underlying architecture. This feature offers new opportunities for robust trapping of light in nano- and micrometre-scale systems subject to fabrication imperfections and environmentally induced deformations. Here, we report lasing in such topological edge states of a one-dimensional lattice of polariton micropillars that implements an orbital version of the Su–Schrieffer–Heeger Hamiltonian. We further demonstrate that lasing in these states persists under local deformations of the lattice. These results open the way to the implementation of chiral lasers in systems with broken time-reversal symmetry and, when combined with polariton interactions, to the study of nonlinear phenomena in topological photonics.

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## Acknowledgements

The authors thank M. Milicevic and G. Montambaux for discussions. This work was supported by the French National Research Agency (ANR) project Quantum Fluids of Light (ANR-16-CE30-0021) and program Labex NanoSaclay via the project ICQOQS (grant no. ANR-10-LABX-0035), the French RENATECH network, the ERC grant Honeypol and the EU-FET Proactive grant AQUS (project no. 640800). P.S.-J. acknowledges financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC).

## Author information

Authors

### Contributions

P.S.-J. performed the experiments with help from V.G., carried out the calculations, analysed the data and wrote the manuscript, with the guidance of J.B. and A.A. T.O. provided critical inputs to the theoretical analysis. E.G., A.L., L.L. and I.S. grew and processed the sample. J.B. and A.A. designed the sample and supervised the work. All authors revised the manuscript.

### Corresponding author

Correspondence to P. St-Jean.

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### Competing interests

The authors declare no competing financial interests.

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## Electronic supplementary material

### Supplementary Information

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St-Jean, P., Goblot, V., Galopin, E. et al. Lasing in topological edge states of a one-dimensional lattice. Nature Photon 11, 651–656 (2017). https://doi.org/10.1038/s41566-017-0006-2

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