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Tunable nanophotonic devices and cavities based on a two-dimensional magnet

Nature Photonics volume 19, pages 1006–1012 (2025)Cite this article

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Abstract

Central to the field of nanophotonics is the ability to engineer the flow of light through nanoscale structures. These structures often have permanent working spectral ranges and optical properties that are fixed during fabrication. Quantum materials, with their correlated and intertwined degrees of freedom, offer a promising avenue for dynamically controlling photonic devices without altering their physical structure. Here we fabricate photonic crystal slabs from CrSBr, a van der Waals antiferromagnetic semiconductor, and demonstrate in situ control over their optical properties. Leveraging the combination of the exceptionally large refractive index of CrSBr near its excitonic resonances and its tunability via external fields, we achieve precise manipulation of photonic modes at near-visible and infrared wavelengths, showcasing a new paradigm for nanophotonic device design. The resulting guided resonances of the photonic crystal are tightly packed in the spectrum with very small mode volumes, are highly tunable via external magnetic fields and exhibit high Q factors exceeding 1,200. These resonances self-hybridize with the excitonic degrees of freedom, resulting in intrinsic strong light–matter coupling. Our findings underscore the potential of quantum materials for developing in situ tunable photonic elements and cavities.

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Fig. 1: Photonic resonances in PhC slabs made of CrSBr.
Fig. 2: Self-hybridized exciton–polaritons in CrSBr photonic crystal slabs.
Fig. 3: In situ tunability of the photonic modes.
Fig. 4: Strongly tunable photonic resonances in the near-visible range.

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Data availability

Raw experimental data used in the article are available via Harvard Dataverse at https://doi.org/10.7910/DVN/1NPBTC.

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Acknowledgements

We acknowledge helpful discussions with M. Butun. This material is based upon work supported by the US Department of Energy, Office of Science National Quantum Information Science Research Center’s Co-design Center for Quantum Advantage (C2QA) under contract number DE-SC0012704 (R.C.). C2QA led in this research. This material is also based upon work sponsored in part by the US Army DEVCOM ARL Army Research Office through the MIT Institute for Soldier Nanotechnologies under Cooperative Agreement number W911NF-23-2-0121 (M.S.). This work was performed in part on the Raith VELION FIB-SEM in the MIT.nano Characterization Facilities (award number DMR-2117609) and in Fab.nano and Characterization.nano facilities at MIT.nano. A.K.D. acknowledges support from MathWorks Science Fellowship.

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  1. These authors contributed equally: Ahmet Kemal Demir, Luca Nessi.

Authors and Affiliations

  1. Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA

    Ahmet Kemal Demir, Luca Nessi, Sachin Vaidya, Connor A. Occhialini, Marin Soljačić & Riccardo Comin

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  1. Ahmet Kemal Demir
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Contributions

A.K.D., L.N. and R.C. conceived the project. A.K.D. performed the nanofabrication and carried out the experiments together with L.N., with help from C.A.O., under the supervision of R.C. S.V., supervised by M.S., and A.K.D. performed the simulations. All authors contributed to the writing of the paper.

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Correspondence to Riccardo Comin.

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Nature Photonics thanks Alexander Khanikaev, Angel Rubio and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–17, Notes 1 and 2 and Table 1.

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Demir, A.K., Nessi, L., Vaidya, S. et al. Tunable nanophotonic devices and cavities based on a two-dimensional magnet. Nat. Photon. 19, 1006–1012 (2025). https://doi.org/10.1038/s41566-025-01712-2

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