Transverse photon spin of bulk electromagnetic waves in bianisotropic media


Photons possess spin degree of freedom, which plays an important role in various applications such as optical communications, information processing and sensing. In isotropic media, photon spin is aligned with the propagation direction of light, obeying the principle of spin momentum locking. Interestingly, surface waves decaying away from an interface have a photon spin transverse to its propagation, opening exciting opportunities for the observation of spin-dependent excitation in confined systems. Here, we propose and realize transverse photon spin (T-spin) in a bulk medium, without relying on the presence of any interfaces. We show the mapping of the T-spin of surface modes to that of the bulk modes by introducing bianisotropy into the medium. We further discover that the interface between two bianisotropic media of opposite orientations supports edge-dependent propagating modes with tunable cutoff frequencies. Our results provide a new platform for manipulating the spin–orbit interaction of electromagnetic waves.

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Fig. 1: T-spins in the bulk mode of a homogeneous medium.
Fig. 2: Demonstration of T-spin in a homogeneous metamaterial.
Fig. 3: Spin locked scattering from a finite-sized bianisotropic metamaterial.
Fig. 4: Interface modes and their propagation characteristics.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


  1. 1.

    Lodahl, P. et al. Chiral quantum optics. Nature 541, 473–480 (2017).

  2. 2.

    Bliokh, K. Y., Smirnova, D. & Nori, F. Quantum spin Hall effect of light. Science 348, 1448–1451 (2015).

  3. 3.

    Bliokh, K. Y., Niv, A., Kleiner, V. & Hasman, E. Geometrodynamics of spinning light. Nat. Photon. 2, 748–753 (2008).

  4. 4.

    Onoda, M., Murakami, S. & Nagaosa, N. Hall effect of light. Phys. Rev. Lett. 93, 083901 (2004).

  5. 5.

    Wang, Z., Chong, Y., Joannopoulos, J. D. & Soljacić, M. Observation of unidirectional backscattering-immune topological electromagnetic states. Nature 461, 772–775 (2009).

  6. 6.

    Haldane, F. D. M. & Raghu, S. Possible realization of directional optical waveguides in photonic crystals with broken time-reversal symmetry. Phys. Rev. Lett. 100, 013904 (2008).

  7. 7.

    Khanikaev, A. B. et al. Photonic topological insulators. Nat. Mater. 12, 233–239 (2013).

  8. 8.

    Rechtsman, M. C. et al. Photonic Floquet topological insulators. Nature 496, 196–200 (2013).

  9. 9.

    Chen, W. J. et al. Experimental realization of photonic topological insulator in a uniaxial metacrystal waveguide. Nat. Commun. 5, 5782 (2014).

  10. 10.

    Cheng, X. et al. Robust reconfigurable electromagnetic pathways within a photonic topological insulator. Nat. Mater. 15, 542–548 (2016).

  11. 11.

    Slobozhanyuk, A. et al. Three-dimensional all-dielectric photonic topological insulator. Nat. Photon. 11, 130–136 (2017).

  12. 12.

    Alpeggiani, F., Bliokh, K. Y., Nori, F. & Kuipers, L. Electromagnetic helicity in complex media. Phys. Rev. Lett. 120, 243605 (2018).

  13. 13.

    Bliokh, K. Y., Leykam, D., Lein, M. & Nori, F. Topological non-Hermitian origin of surface Maxwell waves. Nat. Commun. 10, 580 (2019).

  14. 14.

    Bliokh, K. Y., Bekshaev, A. Y. & Nori, F. Extraordinary momentum and spin in evanescent waves. Nat. Commun. 5, 3300 (2014).

  15. 15.

    Bliokh, K. Y., Rodríguez-Fortuño, F. J., Nori, F. & Zayats, A. V. Spin–orbit interactions of light. Nat. Photon. 9, 796–808 (2015).

  16. 16.

    Antognozzi, M. et al. Direct measurements of the extraordinary optical momentum and transverse spin-dependent force using a nano-cantilever. Nat. Phys. 12, 731–735 (2016).

  17. 17.

    Bliokh, K. Y., Bekshaev, A. Y. & Nori, F. Optical momentum, spin and angular momentum in dispersive media. Phys. Rev. Lett. 119, 073901 (2017).

  18. 18.

    Bliokh, K. Y. & Nori, F. Transverse spin and surface waves in acoustic metamaterials. Phys. Rev. B 99, 020301(R) (2019).

  19. 19.

    Bekshaev, A. Y., Bliokh, K. Y. & Nori, F. Transverse spin and momentum in two-wave interference. Phys. Rev. X 5, 011039 (2015).

  20. 20.

    Junge, C., O’Shea, D., Volz, J. & Rauschenbeutel, A. Strong coupling between single atoms and nontransversal photons. Phys. Rev. Lett. 110, 213604 (2013).

  21. 21.

    Gong, S. H., Alpeggiani, F., Sciacca, B., Garnett, E. C. & Kuipers, L. Nanoscale chiral valley–photon interface through optical spin–orbit coupling. Science 359, 443–447 (2018).

  22. 22.

    Slobozhanyuk, A. P. et al. Enhanced photonic spin Hall effect with subwavelength topological edge states. Laser Photon. Rev. 10, 656–664 (2016).

  23. 23.

    Piao, X., Yu, S. & Park, N. Design of transverse spinning of light with globally unique handedness. Phys. Rev. Lett. 120, 203901 (2018).

  24. 24.

    Neugebauer, M., Eismann, J. S., Bauer, T. & Banzer, P. Magnetic and electric transverse spin density of spatially confined light. Phys. Rev. X 8, 021042 (2018).

  25. 25.

    Picardi, M. F., Zayats, A. V. & Rodriguez-Fortuno, F. J. Janus and Huygens dipoles: near-field directionality beyond spin-momentum locking. Phys. Rev. Lett. 120, 117402 (2018).

  26. 26.

    Gorlach, M. A. et al. Far-field probing of leaky topological states in all-dielectric metasurfaces. Nat. Commun. 9, 909 (2018).

  27. 27.

    Kong, J. A. Electromagnetic Wave Theory (EMW Publishing, 2005).

  28. 28.

    Bliokh, K. Y. & Nori, F. Transverse spin of a surface polariton. Phys. Rev. A 85, 061801 (2012).

  29. 29.

    Bliokh, K. Y. & Nori, F. Transverse and longitudinal angular momenta of light. Phys. Rep. 592, 1–38 (2015).

  30. 30.

    Aiello, A., Banzer, P., Neugebaueru, M. & Leuchs, G. From transverse angular momentum to photonic wheels. Nat. Photon. 9, 789–795 (2015).

  31. 31.

    Mitsch, R., Sayrin, C., Albrecht, B., Schneeweiss, P. & Rauschenbeutel, A. Quantum state-controlled directional spontaneous emission of photons into a nanophotonic waveguide. Nat. Commun. 5, 5713 (2014).

  32. 32.

    Rodriguez-Fortuno, F. J. et al. Near-field interference for the unidirectional excitation of electromagnetic guided modes. Science 340, 328–330 (2013).

  33. 33.

    Lin, J. et al. Polarization-controlled tunable directional coupling of surface plasmon polaritons. Science 340, 331–334 (2013).

  34. 34.

    Kapitanova, P. V. et al. Photonic spin Hall effect in hyperbolic metamaterials for polarization-controlled routing of subwavelength modes. Nat. Commun. 5, 3226 (2014).

  35. 35.

    Shao, Z. K., Zhu, J. B., Chen, Y. J., Zhang, Y. F. & Yu, S. Y. Spin–orbit interaction of light induced by transverse spin angular momentum engineering. Nat. Commun. 9, 926 (2018).

  36. 36.

    Spitzer, F. et al. Routing the emission of a near-surface light source by a magnetic field. Nat. Phys. 14, 1043–1049 (2018).

  37. 37.

    Peng, L. et al. Layer-by-layer design of bianisotropic metamaterial and its homogenization. Prog. Electromagn. Res. 159, 39–47 (2017).

  38. 38.

    Li, Z., Aydin, K. & Ozbay, E. Determination of the effective constitutive parameters of bianisotropic metamaterials from reflection and transmission coefficients. Phys. Rev. E 79, 026610 (2009).

  39. 39.

    Silveirinha, M. & Engheta, N. Tunneling of electromagnetic energy through subwavelength channels and bends using ε-near-zero materials. Phys. Rev. Lett. 97, 157403 (2006).

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This work is financially supported by the National Natural Science Foundation of China (NNSFC) under grants 61875051, 61625502, 61801426, 61574127 and 61372022 and the Top-Notch Young Talents Program of China. S.Z. acknowledges support from an ERC Consolidator Grant (TOPOLOGICAL), the Royal Society and the Wolfson Foundation and Horizon 2020 Action, projects 734578 (D-SPA) and 777714 (NOCTORNO).

Author information

L.P. conceived the idea. L.P. and S.Z. proposed the physical concept, formulated the theory and planned the experiments. L.P., L.D., K.W. and L.Z. conducted the experiments. F.G., G.W., Y.Y. and H.C. participated in the data processing and analysis. L.P., S.Z., F.G. and H.C. discussed the results and wrote the manuscript.

Correspondence to Liang Peng or Hongsheng Chen or Shuang Zhang.

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Supplementary details, discussion, derivations and Figs. 1–11.

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Peng, L., Duan, L., Wang, K. et al. Transverse photon spin of bulk electromagnetic waves in bianisotropic media. Nat. Photonics 13, 878–882 (2019).

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