Exceptional points in three-dimensional plasmonic nanostructures

Kodigala, Ashok; Lepetit, Thomas; Kanté, Boubacar

doi:10.1103/physrevb.94.201103

Cited by 29 publications

(13 citation statements)

References 28 publications

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“…Such dielectric/plasmonic systems are inherently non-Hermitian, and can be designed to possess an effective-PT phase transition -full PT -symmetric properties can then be recovered by reintroducing gain [22,23]. Despite its great potential in a multitude of areas [10], and a growing number of studies [22][23][24][25][26], to the best of our knowledge effective PTphase transitions, tuned across the EP, have yet to be experimentally reported in plasmonic waveguides. Here, we experimentally observe the effective PT -phase transition across the plasmonic EP of a tuneable hybrid dielectric/plasmonic waveguide system.…”

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confidence: 99%

Tuning the Effective PT Phase of Plasmonic Eigenmodes

2019

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We experimentally observe an effective PT -phase transition through the exceptional point in a hybrid plasmonic-dielectric waveguide system. Transmission experiments reveal fundamental changes in the underlying Eigenmode interactions as the environmental refractive index is tuned, which can be unambiguously attributed to a crossing through the plasmonic exceptional point. These results extend the design opportunities for tuneable non-Hermitian physics to plasmonic systems.Hermitian systems and their operators are used to describe a wide range of physical phenomena to predict the evolution of Eigenstates via unitary operations containing purely real Eigenvalues [1,2]. Recently, increasing attention has been dedicated to non-Hermitian systems, which are non-conservative and generally yield complex Eigenvalue spectra [3]. Non-Hermitian systems are typically created by opening a Hermitian system to the environment by including dissipation and/or gain. Interestingly, coupled non-Hermitian systems can yield purely real Eigenvalues which respect parity-time (PT ) symmetry via an appropriate balance of gain and loss [4,5]. In an unbalanced scenario, a PT -broken system shows complex conjugate Eigenvalue pairs. The PT -symmetric (PTS) and PT -broken (PTB) regimes are separated by the exceptional point (EP), where the Eigenvalues coalesce, which is associated with several interesting physical phenomena, such as level repulsion [6], reflectionless propagation [7], and topological phase transitions [8].

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confidence: 99%

Tuning the Effective PT Phase of Plasmonic Eigenmodes

2019

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“…Exceptional points in wave resonators of different origin arise when both spectral positions and linewidths of two resonances coincide and the corresponding spatial modes coalesce into one [1,2]. Originally identified as an inherent property of non-Hermitian quantum systems [3-5], exceptional points have become a focus of intense research in classical systems with gain and loss [6], such as optical cavities [7], microwave resonators [8,15], and plasmonic nanostructures [9]. The counterintuitive behaviour of a wave system in the vicinity of an exceptional point led to demonstrations of a range of peculiar phenomena, including enhanced loss-assisted lasing [10,11], unidirectional transmission of signals [12], and loss-induced transparency [13].Due to the nontrivial topology of the exceptional point, the two eigenstates coalesce with a phase difference of ± π/2, which results in a well-defined handedness (chirality) of the surviving eigenstate [14].…”

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confidence: 99%

Chiral Modes at Exceptional Points in Exciton-Polariton Quantum Fluids

Gao

Estrecho

et al. 2018

Phys. Rev. Lett.

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We demonstrate generation of chiral modes -vortex flows with fixed handedness in excitonpolariton quantum fluids. The chiral modes arise in the vicinity of exceptional points (non-Hermitian spectral degeneracies) in an optically-induced resonator for exciton polaritons. In particular, a vortex is generated by driving two dipole modes of the non-Hermitian ring resonator into degeneracy. Transition through the exceptional point in the space of the system's parameters is enabled by precise manipulation of real and imaginary parts of the closed-wall potential forming the resonator. As the system is driven to the vicinity of the exceptional point, we observe the formation of a vortex state with a fixed orbital angular momentum (topological charge). Our method can be extended to generate high-order orbital angular momentum states through coalescence of multiple non-Hermitian spectral degeneracies, which could find application in integrated optoelectronics.Introduction. Exceptional points in wave resonators of different origin arise when both spectral positions and linewidths of two resonances coincide and the corresponding spatial modes coalesce into one [1,2]. Originally identified as an inherent property of non-Hermitian quantum systems [3][4][5], exceptional points have become a focus of intense research in classical systems with gain and loss [6], such as optical cavities [7], microwave resonators [8,15], and plasmonic nanostructures [9]. The counterintuitive behaviour of a wave system in the vicinity of an exceptional point led to demonstrations of a range of peculiar phenomena, including enhanced loss-assisted lasing [10,11], unidirectional transmission of signals [12], and loss-induced transparency [13].Due to the nontrivial topology of the exceptional point, the two eigenstates coalesce with a phase difference of ± π/2, which results in a well-defined handedness (chirality) of the surviving eigenstate [14]. This remarkable property of the eigenstate at the exceptional point was first experimentally demonstrated in a microwave cavity [15] and, very recently, led to observation of directional lasing in optical micro-resonators [16,17]. So far, the chirality of the unique eigenstate at an exceptional point has not been demonstrated in any quantum system.In this work, we demonstrate formation of a chiral state at an exceptional point in a macroscopic quantum system of condensed exciton polaritons. Exciton polaritons are hybrid light-matter bosonic quasiparticles arising due to strong coupling between excitons and photons in semiconductor microcavities [18,19]. Once sufficient density of exciton polaritons is injected by an optical or electrical pump, the transition to quantum degeneracy occurs, whereby typical signatures of a Bose-Einstein con-

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“…We note, however, that the true applicability and usefulness of EP sensing depend on the details of how the parametric change is measured [8,11]. In any case, finding practically useful EPs in physically accessible systems [12][13][14] and parameter regimes is still an open problem [15][16][17], and a range of candidates have been studied, such as parity-timesymmetric systems [12,[18][19][20][21][22][23][24][25], coupled atom-cavity systems [26], microcavities [12,20,21,[27][28][29], microwave cavities [30][31][32][33], acoustic systems [34], photonic lattices [19,35], photonic crystal slabs [36], exciton-polariton billiards [37], plasmonic nanoresonators [38], ring resonator [39], optical resonators [40][41][42], and topological arrangements [37]. However, the typical size of these systems possessing EPs is usually too large (of several hundred nanometers) to be utilized for sensing in some important applications.…”

Section: Introductionmentioning

confidence: 99%

Collectively induced exceptional points of quantum emitters coupled to nanoparticle surface plasmons

et al. 2020

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Exceptional points, resulting from non-Hermitian degeneracies, have the potential to enhance the capabilities of quantum sensing. Thus, finding exceptional points in different quantum systems is vital for developing such future sensing devices. Taking advantage of the enhanced light-matter interactions in a confined volume on a metal nanoparticle surface, here we theoretically demonstrate the existence of exceptional points in a system consisting of quantum emitters coupled to a metal nanoparticle of subwavelength scale. By using an analytical quantum electrodynamics approach, exceptional points are manifested as a result of a strong coupling effect and observable in a drastic splitting of originally coalescent eigenenergies. Furthermore, we show that exceptional points can also occur when a number of quantum emitters is collectively coupled to the dipole mode of localized surface plasmons. Such a quantum collective effect not only relaxes the strong-coupling requirement for an individual emitter, but also results in a more stable generation of the exceptional points. Furthermore, we point out that the exceptional points can be explicitly revealed in the power spectra. A generalized signal-to-noise ratio, accounting for both the frequency splitting in the power spectrum and the system's dissipation, shows clearly that a collection of quantum emitters coupled to a nanoparticle provides a better performance of detecting exceptional points, compared to that of a single quantum emitter. arXiv:1904.08133v2 [cond-mat.mes-hall] 5 Jan 2020

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Exceptional points in three-dimensional plasmonic nanostructures

Cited by 29 publications

References 28 publications

Tuning the Effective PT Phase of Plasmonic Eigenmodes

Tuning the Effective PT Phase of Plasmonic Eigenmodes

Chiral Modes at Exceptional Points in Exciton-Polariton Quantum Fluids

Collectively induced exceptional points of quantum emitters coupled to nanoparticle surface plasmons

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