# Observation of an exceptional point in a non-Hermitian metasurface

@article{Park2020ObservationOA, title={Observation of an exceptional point in a non-Hermitian metasurface}, author={Sang Hyun Park and Sung-Gyu Lee and Soojeong Baek and Taewoo Ha and Sanghyub Lee and Bumki Min and Shuang Zhang and Mark Lawrence and Teun-Teun Kim}, journal={Nanophotonics}, year={2020}, volume={9}, pages={1031 - 1039} }

Abstract Exceptional points (EPs), also known as non-Hermitian degeneracies, have been observed in parity-time symmetric metasurfaces as parity-time symmetry breaking points. However, the parity-time symmetry condition puts constraints on the metasurface parameter space, excluding the full examination of unique properties that stem from an EP. Here, we thus design a general non-Hermitian metasurface with a unit cell containing two orthogonally oriented split-ring resonators (SRRs) with…

## 14 Citations

Exceptional points in metasurface

- PhysicsInfrared and Laser Engineering
- 2020

Exceptional points are special points in non-Hermitian systems, and there are many novel physical phenomena in the parameter space near the exceptional points. In recent years, metasurface has been a…

Exceptional points in Fermi liquids with quadrupolar interactions

- Physics, Mathematics
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We show the existence of non-Hermitian degeneracies, known as exceptional points, in the collective mode spectrum of Fermi liquids with quadrupolar interactions. Through a careful analysis of the…

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Nanophotonics considers the complex interactions between light and matter at the sub-wavelength scale. Recent progress in nanophotonics has revealed unprecedented optical phenomena, which have opened…

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. We consider the scattering of electromagnetic waves by non-spherical dielectric resonators and reveal that it can be linked to the exceptional points underpinned by the physics of non-Hermitian…

Experimental Demonstration of the Non‐Hermitian Radio Frequency Metasurface with Polarization‐Dependent Unidirectional Reflectionless Propagation

- PhysicsAdvanced Photonics Research
- 2022

Unidirectional reflectionlessness is one of the most fascinating effects at the exceptional point (EP) in a non‐Hermitian system. Herein, a polarization‐dependent non‐Hermitian radio frequency…

Non-Hermitian Squeezed Polarons

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- 2022

Recent experimental breakthroughs in non-Hermitian ultracold atomic lattices have dangled tantalizing prospects in realizing exotic, hitherto unreported many-body non-Hermitian quantum phenomena. In…

Extreme Diffraction Control in Metagratings Leveraging Bound States in the Continuum and Exceptional Points

- PhysicsLaser & Photonics Reviews
- 2022

Coupled resonances in non‐Hermitian systems can lead to exotic optical features, such as bound states in the continuum (BICs) and exceptional points (EPs), which have been recently emerged as…

Plasmonic topological metasurface by encircling an exceptional point

- Materials ScienceScience
- 2021

A topologically protected full 2π-phase on a specific reflected polarization channel is engineered that brings topological properties into the realm of industrial applications at optical frequencies and proves that metasurface technology represents a convenient test bench to study and validate topological photonic concepts.

Non-Hermitian Electromagnetic Metasurfaces at Exceptional Points

- Physics
- 2021

Exceptional points are spectral singularities in non-Hermitian systems at which two or more eigenvalues and their corresponding eigenvectors simultaneously coalesce. Originating from quantum theory,…

## References

SHOWING 1-10 OF 37 REFERENCES

Manifestation of PT symmetry breaking in polarization space with terahertz metasurfaces.

- PhysicsPhysical review letters
- 2014

This work investigates parity time symmetry breaking in polarization space using a metasurface with anisotropic absorption, whose building blocks consist of two orthogonally orientated meta-atoms with the same resonant frequency but different loss coefficients.

Enhanced sensitivity at higher-order exceptional points

- PhysicsNature
- 2017

Higher-order exceptional points are observed in a coupled cavity arrangement—specifically, a ternary, parity–time-symmetric photonic laser molecule—with a carefully tailored gain–loss distribution and it is found that the frequency response follows a cube-root dependence on induced perturbations in the refractive index.

Encircling an exceptional point.

- PhysicsPhysical review. E, Statistical, nonlinear, and soft matter physics
- 2004

The geometric phases that occur when an EP is encircled four times are measured and it is confirmed that for this system anEP is a branch point of fourth order.

Experimental observation of the topological structure of exceptional points.

- PhysicsPhysical review letters
- 2001

A microwave cavity experiment where exceptional points (EPs), which are square root singularities of the eigenvalues as function of a complex interaction parameter, are encircled in the laboratory and one of the Eigenvectors undergoes a sign change which can be discerned in the field patterns.

Exceptional points in optics and photonics

- PhysicsScience
- 2019

The topic of exceptional points in photonics is reviewed and some of the possible exotic behavior that might be expected from engineering such systems are explored, as well as new angle of utilizing gain and loss as new degrees of freedom, in stark contrast with the traditional approach of avoiding these elements.

Time-asymmetric loop around an exceptional point over the full optical communications band

- PhysicsNature
- 2018

Time-asymmetric light transmission over the entire optical communications band is achieved using a silicon photonic structure with photonic modes that dynamically encircle an exceptional point in the optical domain using a semiconductor platform with controllable optoelectronic properties.

Observation of non-Hermitian degeneracies in a chaotic exciton-polariton billiard

- PhysicsNature
- 2015

It is demonstrated that non-Hermiticity dramatically modifies the structure of modes and spectral degeneracies in exciton-polariton systems, and, therefore, will affect their quantum transport, localization and dynamical properties.

PT symmetry and spontaneous symmetry breaking in a microwave billiard.

- PhysicsPhysical review letters
- 2012

We demonstrate the presence of parity-time (PT) symmetry for the non-Hermitian two-state Hamiltonian of a dissipative microwave billiard in the vicinity of an exceptional point (EP). The shape of the…

The physics of exceptional points

- Physics
- 2012

A short résumé is given about the nature of exceptional points (EPs) followed by discussions about their ubiquitous occurrence in a great variety of physical problems. EPs feature in classical as…

Non-Hermitian photonics based on parity–time symmetry

- Physics
- 2017

Nearly one century after the birth of quantum mechanics, parity–time symmetry is revolutionizing and extending quantum theories to include a unique family of non-Hermitian Hamiltonians. While…