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Non-Hermitian systems have attracted significant interest because of their intriguing properties, including exceptional points (EPs), where eigenvalues and the corresponding eigenstates coalesce. In particular, quantum systems with EPs exhibit an enhanced sensitivity to external perturbations, which increases with the order of the EP. Therefore, higher-order EPs hold significant potential for advanced sensing applications, but they are challenging to achieve due to stringent symmetry requirements. In this work, we study the dynamics of a generalized lossy waveguide beam splitter with asymmetric coupling by introducing non-reciprocity as a tunable parameter to achieve higher-order EPs even without dissipation. Moreover, we analyze the evolution of NOON-states under activated non-reciprocity, highlighting its impact on quantum systems. Our results open new pathways for realizing higher-order EPs in non-reciprocal open quantum systems.
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This content will become publicly available on April 1, 2027
Exceptional points in plasmonics: Fundamentals, platforms, and applications
Exceptional points (EPs), representing non-Hermitian singularities where eigenvalues and eigenvectors coalesce, have emerged as an intriguing concept in modern physics. Their unique topological and asymmetric responses have enabled new pathways for controlling wave propagation, sensing, and signal processing. Among the diverse platforms, plasmonic systems have proven especially attractive, as their inherent loss, strong dispersion, and tunable resonances and coupling can be utilized to tailor EPs at the subwavelength scale. In this review, we provide a comprehensive overview of recent advances at the intersection of EP physics and plasmonics. We first introduce the mathematical and physical foundations of EPs in non-Hermitian systems. We then discuss key experimental and theoretical developments in plasmonic EPs, including polarization manipulation, asymmetric wavefront control, mode conversion, and enhanced sensitivity. Particular attention is given to strategies that exploit symmetry breaking, loss engineering, and geometric phases to realize novel and robust EP-driven functionalities. Finally, we discuss emerging trends, such as the use of EP pairs for full vectorial control and the integration of non-Hermitian plasmonic structures with tunable, active, and even nonreciprocal thermal emission. By reframing loss as a design resource and leveraging the Riemann-surface geometry of non-Hermitian spectra, plasmonic EPs offer a new route to compact, robust, and programmable nanophotonic devices.
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- PAR ID:
- 10689661
- Publisher / Repository:
- American Institute of Physics (AIP)
- Date Published:
- Journal Name:
- Applied Physics Reviews
- Volume:
- 13
- Issue:
- 2
- ISSN:
- 1931-9401
- Page Range / eLocation ID:
- 021303
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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