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Fundamental optical phenomena of strongly anisotropic polaritons at the nanoscale

Nature Nanotechnology volume 21, pages 23–38 (2026)Cite this article

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Abstract

Polaritons are hybrid quasiparticles consisting of photons and electric (or magnetic) dipole-carrying excitations. Their observation has advanced our understanding of light–matter interactions and led to the manipulation of energy flows at the nanoscale. The discovery of strongly anisotropic van der Waals materials and the almost simultaneous development of near-field imaging techniques have led to the observation of a variety of highly confined polaritons with exotic properties, such as unidirectional, diffractionless or ray-like propagation, and hyperbolic dispersion. In this Review, we highlight the fundamental optical phenomena that have been redefined by these anisotropic polaritons, including anomalous cases of refraction, reflection and focusing. These phenomena promise unprecedented control over light–matter interactions at the nanoscale in spectral regions spanning from the visible to the terahertz. We also review strategies to manipulate these polaritons and offer our perspective on the challenges facing polaritonic research over the coming years towards practical applications.

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Fig. 1: Exotic refractions of anisotropic polaritons at the nanoscale.
Fig. 2: Exotic reflections of anisotropic polaritons at the nanoscale.
Fig. 3: Focusing of polaritons in isotropic and anisotropic media.
Fig. 4: Potential nanophotonic applications of anisotropic polaritons.

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Acknowledgements

This work is supported by the Beijing Natural Science Foundation (grant number Z240005), the National Natural Science Foundation of China (grant numbers 12474027, 12404437, 12374294, 12321004, 52488301, T2325005 and 62375016) and the National Key R&D Program of China (numbers 2023YFA1407600, 2021YFA1400602 and 2024YFB2809204). P.A.G. acknowledges support from the European Research Council under Consolidator grant number 101044461, TWISTOPTICS, the Spanish Ministry of Science and Innovation (State Plan for Scientific and Technical Research and Innovation grant number PID2022-141304NB-I00) and the Asturias FICYT under grant AYUD/2021/51185 with the support of FEDER funds. J.M.S. acknowledges financial support from the Spanish Ministry of Science and Innovation (grant number PID2023-148457NB-I00 funded by MCIN/AEI/10.13039/501100011033 and FSE+, PCI2022-132953 funded by MCIN/AEI/10.13039/501100011033 and the EU “NextGenerationEU”/PRTR, CNS2024-154342 funded by MICIU/AEI/10.13039/501100011033). A.Y.N. acknowledges the Spanish Ministry of Science and Innovation (PID2023-147676NB-I00), the Basque Department of Education (PIBA-2023-1-0007) and the Basque Department of Education (PIBA-2023-1-0007 and IKUR strategy).

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Author notes

  1. These authors contributed equally: Yixi Zhou, Zhiwei Guo, Aitana Tarazaga Martín-Luengo, Christian Lanza.

Authors and Affiliations

  1. State Key Laboratory of Chips and Systems for Advanced Light Field Display, MOE Key Lab of Advanced Optoelectronic Quantum Architecture And Measurement, School of Physics, Beijing Institute of Technology, Beijing, China

    Yixi Zhou, Chengguang Yu, Chongrui Li, Weixiang Xia, Xiaoyang Duan, Yang Wang, Yugui Yao, Jiafang Li & Jiahua Duan

  2. Beijing Key Laboratory of Nano-Photonics and Nano-Structure (NPNS), Department of Physics, Capital Normal University, Beijing, China

    Yixi Zhou

  3. MOE Key Laboratory of Advanced Micro-Structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai, China

    Zhiwei Guo

  4. Department of Physics, University of Oviedo, Oviedo, Spain

    Aitana Tarazaga Martín-Luengo, Christian Lanza, José Álvarez Cuervo, Javier Martín-Sánchez, Pablo Alonso-Gonzalez & Jiahua Duan

  5. Istituto Italiano di Tecnologia, Center for Biomolecular Nanotechnologies, Arnesano, Italy

    Gonzalo Álvarez-Pérez

  6. Center of Research on Nanomaterials and Nanotechnology, CINN (CSIC-Universidad de Oviedo), El Entrego, Spain

    José Álvarez Cuervo & Pablo Alonso-Gonzalez

  7. Donostia International Physics Center (DIPC), Donostia/San Sebastián, Spain

    Alexey Y. Nikitin

  8. IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

    Alexey Y. Nikitin

  9. Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, China

    Yugui Yao

  10. International Center for Quantum Materials, Beijing Institute of Technology, Zhuhai, China

    Yugui Yao

Authors
  1. Yixi Zhou
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  2. Zhiwei Guo
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Contributions

J.D. and P.A.G. conceived the work. Y.Z. and Z.G. wrote the first version of the manuscript. A.T.M.-L. contributed to Figs. 1 and 2, and the figure in Box 2. C. Lanza, C. Y. and W.X. contributed to the analytical calculations in the figures in Boxes 1 and 2 and Figs. 1 and 2. G.A.-P. contributed to the ‘Optical phenomena of strongly anisotropic polaritons at the nanoscale’ section. C. Li, X.D. and Y.W. contributed to the figure in Box 1 and Figs. 3 and 4. J.M.S., J.A.C., A.Y.N. and Y.Y. contributed to the discussion of content. J.D., P.A.G. and J.L. supervised the project. All authors contributed to the editing of the paper.

Corresponding authors

Correspondence to Jiafang Li, Pablo Alonso-Gonzalez or Jiahua Duan.

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Nature Nanotechnology thanks Siyuan Dai and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Zhou, Y., Guo, Z., Tarazaga Martín-Luengo, A. et al. Fundamental optical phenomena of strongly anisotropic polaritons at the nanoscale. Nat. Nanotechnol. 21, 23–38 (2026). https://doi.org/10.1038/s41565-025-02039-3

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