Symmetry-breaking-induced plasmonic exceptional points and nanoscale sensing


Singularities of open systems, known as exceptional points (EPs), have been shown to exhibit increased sensitivities, but the observation of EPs has so far been limited to wavelength-scaled systems subject to the diffraction limit. Plasmons, the collective oscillations of free electrons coupled to photons, shrink the wavelength of light to electronic and molecular length scales. We propose a novel approach to EPs based on spatial symmetry breaking and report their observation in plasmonics at room temperature. The plasmonic EPs are based on the hybridization of detuned resonances in multilayered plasmonic structures to reach a critical complex coupling rate between nanoantenna arrays, resulting in the simultaneous coalescence of the resonances and loss rates. Their utility as sensors of anti-immunoglobulin G, the most abundant immunoglobulin isotype in human serum, is evaluated. Our work opens the way to a new class of nanoscale devices, sensors and imagers based on topological polaritonic effects.

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Fig. 1: Multilayered periodic plasmonic structure supporting EPs.
Fig. 2: Plasmonic and symmetry-dependent hybridization scheme of resonances and loss rates.
Fig. 3: Experimental observation of plasmonic EP.
Fig. 4: Immuno-assay nanosensing with a plasmonic EP.

Data availability

The data presented in Figs. 2g,h, 3a–d and 4 are available as Source Data. All other data that support the plots within this paper and other findings of this study are available from the corresponding author on reasonable request.

Code availability

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


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This research was supported by the National Science Foundation Career Award (ECCS-1554021) and the Office of Naval Research Young Investigator Award (N00014-17-1-2671) and the ONR JTO MRI Award (N00014-17-1-2442). The work was partially supported by the DARPA DSO-NLM Program no. HR00111820038 and the US Department of Energy (DOE) (grant no. DE-EE0007341). The work was performed in part at the San Diego Nanotechnology Infrastructure, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (grant no. ECCS-1542148). We thank M. Montero for technical assistance regarding the fabrication.

Author information

B.K. conceived the project and guided the theoretical and experimental investigations. J.-H.P. and L.-Y.H. performed the simulations. J.-H.P. fabricated the samples. A.N. developed the setup and performed the measurements with J.-H.P. W.C. functionalized the samples under the guidance of Y.-H.L. and B.K. All authors contributed to discussions and manuscript writing.

Correspondence to Boubacar Kanté.

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The Regents of the University of California have filed a patent application (US Prov. App. 62/823,158) on technology related to the processes described in this article.

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Peer review information Nature Physics thanks Christos Argyropoulos, Jan Wiersig and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–21.

Source data

Source Data Fig. 2

Data of Fig. 2g,h

Source Data Fig. 3

Data of Fig. 3a–d

Source Data Fig. 4

Data of Fig. 4

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Park, J., Ndao, A., Cai, W. et al. Symmetry-breaking-induced plasmonic exceptional points and nanoscale sensing. Nat. Phys. (2020).

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