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

    ADS  Article  Google Scholar 

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

    ADS  MathSciNet  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

  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).

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

  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).

    Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    Google Scholar 

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

    ADS  Article  Google Scholar 

  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).

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

  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).

    Google Scholar 

  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).

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

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

    ADS  Article  Google Scholar 

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

    ADS  MathSciNet  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

  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).

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

  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).

    ADS  Article  Google Scholar 

  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).

    ADS  Article  Google Scholar 

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

    Article  Google Scholar 

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

    Article  Google Scholar 

  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).

    ADS  Article  Google Scholar 

  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).

    ADS  Article  Google Scholar 

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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).

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Authors and Affiliations



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.

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Correspondence to Liang Peng, 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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