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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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.
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.
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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Park, J., Ndao, A., Cai, W. et al. Symmetry-breaking-induced plasmonic exceptional points and nanoscale sensing. Nat. Phys. (2020). https://doi.org/10.1038/s41567-020-0796-x