Observation of exceptional points in reconfigurable non-Hermitian vector-field holographic lattices

Hahn, Choloong; Choi, Young-Sun; Yoon, Jae Woong; Song, Seok Ho; Oh, Cha Hwan; Berini, Pierre

doi:10.1038/ncomms12201

Cited by 57 publications

(65 citation statements)

References 37 publications

(56 reference statements)

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“…The observable signatures of hybridization, level repulsion and line width evolution, are actually related to the presence of an exceptional point (EP) in the eigenspectrum -a branch point where the eigenmodes and eigenvectors coalesce [123]. EPs plays an important role in many physical systems [124][125][126][127][128][129][130][131][132] and, the mathematical origin of the magnon-photon EP can be easily understood by examining the hybridized dispersion. If the damping and coupling strength parameters are allowed to vary it is possible that the square root argument will become zero, and therefore the eigenmodes will become degenerate.…”

Section: Exceptional Points and Hybridizationmentioning

confidence: 99%

Cavity Spintronics: An Early Review of Recent Progress in the Study of Magnon–Photon Level Repulsion

Harder

2018

Solid State Physics

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Light-matter interactions lie at the heart of condensed matter physics, providing physical insight into material behaviour while enabling the design of new devices. Perhaps this is most evident in the push to develop quantum information and spintronic technologies. On the side of quantum information, engineered lightmatter interactions offer a powerful means to access and control quantum states, while at the same time new insights into spin-photon manipulation will benefit the development of spintronic technologies. In this context the recent discovery of hybridization between ferromagnets and cavity photons has ushered in a new era of light-matter exploration at the crossroads of quantum information and spintronics. The key player in this rapidly developing field of cavity spintronics is a quasiparticle, the cavity-magnon-polariton. In this early review of recent work the fundamental behaviour of the cavity-magnon-polariton is summarized and related to the development of new spintronic applications. In the last few years a comprehensive theoretical framework of spin-photon hybridization has been developed. On an intuitive level many features can be described by a universal model of coupled oscillators, however the true origin of hybridization is only revealed by considering a more comprehensive electrodynamic framework. Here both approaches are summarized and an outline of a quantum description through the input-output formalism is provided. Based on this foundation, in depth experimental investigations of the coupled spin-photon system have been performed. For example, it has been found that hybridization will influence spin current generated through the spin pumping mechanism, demonstrating a firm link between spin-photon coupling and spintronics. Furthermore several in-situ coupling control mechanisms, which offer both physical insight and a means to develop cavityspintronic technologies, have been revealed. The many recent developments within this field represent only the first steps in what appears to be a bright future for cavity spintronics. Hopefully this early review will introduce new explorers to this exciting frontier of condensed matter research, lying at the crossroads of magnetism and cavity quantum electrodynamics.

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Section: Exceptional Points and Hybridizationmentioning

confidence: 99%

Cavity Spintronics: An Early Review of Recent Progress in the Study of Magnon–Photon Level Repulsion

Harder

2018

Solid State Physics

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“…When gain and loss are added to the phase modulation in a PT-symmetric fashion within the time window, unidirectional invisibility occurs at EPs. Hahn et al first observed totally asymmetric diffraction in a PTsymmetric photonic lattice at EPs using vector-field holographic interference of two elliptically polarized pump beams on azobenzene-doped polymer thin films [47].…”

Section: Unidirectional Reflectionless Propagation In Pt-symmetric Symentioning

confidence: 99%

Unidirectional reflectionless light propagation at exceptional points

et al. 2017

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Abstract:In this paper, we provide a comprehensive review of unidirectional reflectionless light propagation in photonic devices at exceptional points (EPs). EPs, which are branch point singularities of the spectrum, associated with the coalescence of both eigenvalues and corresponding eigenstates, lead to interesting phenomena, such as level repulsion and crossing, bifurcation, chaos, and phase transitions in open quantum systems described by non-Hermitian Hamiltonians. Recently, it was shown that judiciously designed photonic synthetic matters could mimic the complex non-Hermitian Hamiltonians in quantum mechanics and realize unidirectional reflection at optical EPs. Unidirectional reflectionlessness is of great interest for optical invisibility. Achieving unidirectional reflectionless light propagation could also be potentially important for developing optical devices, such as optical network analyzers. Here, we discuss unidirectional reflectionlessness at EPs in both parity-time (PT)-symmetric and non-PT-symmetric optical systems. We also provide an outlook on possible future directions in this field.

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“…Both the real and imaginary parts of the eigenvalues coalesce at this point. The EPs have been observed in many photonic systems, such as optical microcavities [29,30], coupled optical waveguides [31][32][33], photonic crystal slabs [34][35][36][37] and unidirectionally coupled resonators [38,39]. Many novel properties are also found at or near the EPs, such as loss-induced suppression and revival of lasing [40][41][42], unidirectional transmission or reflection [43][44][45][46][47][48], topological chirality [49][50][51] and laser mode selectivity [52][53][54].…”

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confidence: 99%

Vector Exceptional Points with Strong Superchiral Fields

Zhang

et al. 2020

Phys. Rev. Lett.

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Exceptional points (EPs)，branch points of complex energy surfaces at which eigenvalues and eigenvectors coalesce, are ubiquitous in non-Hermitian systems. Many novel properties and applications have been proposed around the EPs. One of the important applications is to enhance the detection sensitivity. However, due to the lack of single-handed superchiral fields, all of the proposed EP-based sensing mechanisms are only useful for the non-chiral discrimination. Here, we propose theoretically and demonstrate experimentally a new type of EP, which is a called radiation vector EP, to fulfill the homogeneous superchiral fields for chiral sensing. This type of EP is realized by suitably tuning the coupling strength and radiation losses for a pair of orthogonal polarization modes in the photonic crystal slab. Based on the unique modal-coupling property at the vector EP, we demonstrate that the uniform superchiral fields can be generated with two beams of lights illuminating on the photonic crystal slab from opposite directions. Thus, the designed photonic crystal slab, which supports the vector EP, can be used to perform surface-enhanced chiral detection. Our findings provide a new strategy for ultrasensitive characterization and quantification of molecular chirality, a key aspect for various bioscience and biomedicine applications.

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Observation of exceptional points in reconfigurable non-Hermitian vector-field holographic lattices

Cited by 57 publications

References 37 publications

Cavity Spintronics: An Early Review of Recent Progress in the Study of Magnon–Photon Level Repulsion

Cavity Spintronics: An Early Review of Recent Progress in the Study of Magnon–Photon Level Repulsion

Unidirectional reflectionless light propagation at exceptional points

Vector Exceptional Points with Strong Superchiral Fields

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