Crossing of the Branch Cut: The Topological Origin of a Universal 2π‐Phase Retardation in Non‐Hermitian Metasurfaces

Colom, Rémi; Mikheeva, Elena; Achouri, Karim; Zúñiga‐Pérez, Jesús; Bonod, Nicolas; Martin, Olivier J. F.; Burger, Sven; Genevet, Patrice

doi:10.1002/lpor.202200976

Cited by 22 publications

(10 citation statements)

References 79 publications

(118 reference statements)

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“…Incidentally, this presence of a zero in the upper plane, resulting in a so‐called discontinuity branch bridging the zero and a pole across the real frequency axis, has recently been shown to shed new light on the design of Huygens metasurfaces. [ 71 ]…”

Section: Reflectionless Exceptional Points Without Mirror Symmetrymentioning

confidence: 99%

Covert Scattering Control in Metamaterials with Non‐Locally Encoded Hidden Symmetry

Sol,

Röntgen,

del Hougne

2023

Advanced Materials

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Symmetries and tunability are of fundamental importance in wave scattering control, but symmetries are often obvious upon visual inspection which constitutes a significant vulnerability of metamaterial wave devices to reverse‐engineering risks. Here, it is theoretically and experimentally shown that a symmetry in the reduced basis of the “primary meta‐atoms” that are directly connected to the outside world is sufficient; meanwhile, a suitable topology of non‐local interactions between them, mediated by the internal “secondary” meta‐atoms, can hide the symmetry from sight in the canonical basis. Covert symmetry‐based scattering control in a cable‐network metamaterial featuring a hidden parity () symmetry in combination with hidden‐‐symmetry‐preserving and hidden‐‐symmetry‐breaking tuning mechanisms is experimentally demonstrated. Physical‐layer security in wired communications is achieved, using the domain‐wise hidden ‐symmetry as shared secret between the sender and the legitimate receiver. Within the approximation of negligible absorption, the first tuning of a complex scattering metamaterial without mirror symmetry to feature exceptional points (EPs) of ‐symmetric reflectionless states, as well as quasi‐bound states in the continuum, is reported. These results are reproduced in metamaterials involving non‐reciprocal interactions between meta‐atoms, including the first observation of reflectionless EPs in a non‐reciprocal system.This article is protected by copyright. All rights reserved

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Section: Reflectionless Exceptional Points Without Mirror Symmetrymentioning

confidence: 99%

Covert Scattering Control in Metamaterials with Non‐Locally Encoded Hidden Symmetry

Sol,

Röntgen,

del Hougne

2023

Advanced Materials

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“…The SEM has received a renewed interest in the recent years in the case of simple poles, i.e. singularities of order 1, where accurate expressions have been derived and applied to various problems [34][35][36][37][38][39]. In addition, pole or singularity expansions have been increasingly used in the framework of quasi-normal modes or resonant state expansions [40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

Multiple-order singularity expansion method

Ben Soltane,

Colom,

Dierick

et al. 2023

New J. Phys.

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Physical systems and signals are often characterized by complex functions of frequency in the harmonic-domain. The extension of such functions to the complex frequency plane has been a topic of growing interest as it was shown that specific complex frequencies could be used to describe both ordinary and exceptional physical properties. In particular, expansions and factorized forms of the harmonic-domain functions in terms of their poles and zeros under multiple physical considerations have been used. In this work, we start from a general property of continuity and differentiability of the complex functions to derive the multiple-order singularity expansion method. We rigorously derive the common singularity and zero expansion and factorization expressions, and generalize them to the case of singularities of arbitrary order, whilst deducing the behaviour of these complex frequencies from the simple hypothesis that we are dealing with physically realistic signals.

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“…The SEM has received a renewed interest in the recent years in the case of simple poles, i.e. singularities of order 1, where accurate expressions have been derived and applied to various problems [35][36][37][38][39][40]. In addition, pole or singularity expansions have been increasingly used in the frame of quasi-normal modes or resonant state expansions [41][42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%