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Spatio-temporal coupled mode theory for nonlocal metasurfaces

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Light(Science & Applications) 2024年第2期13卷 267-282页

作者： Adam Overvig Sander A.Mann andrea alù Photonics Initiative Advanced Science Research CenterCity University of New YorkNew YorkNY10031USA Physics Program Graduate Center of the City University of New YorkNew YorkNY10016USA

Diffractive nonlocal metasurfaces have recently opened a broad range of exciting developments in nanophotonics research and applications,leveraging spatially extended—yet locally patterned—resonant modes to control light with new degrees of *** conventional grating responses are elegantly captured by temporal coupled mode theory,current approaches are not well equipped to capture the arbitrary spatial response observed in the nascent field of nonlocal ***,we introduce spatio-temporal coupled mode theory(STCMT),capable of elegantly capturing the key features of the resonant response of wavefront-shaping nonlocal *** framework can quantitatively guide nonlocal metasurface design while maintaining compatibility with local metasurface frameworks,making it a powerful tool to rationally design and optimize a broad class of ultrathin optical *** validate this STCMT framework against full-wave simulations of various nonlocal metasurfaces,demonstrating that this tool offers a powerful semi-analytical framework to understand and model the physics and functionality of these devices,without the need for computationally intense full-wave *** also discuss how this model may shed physical insights into nonlocal phenomena in photonics and the functionality of the resulting *** a relevant example,we showcase STCMT’s flexibility by applying it to study and rapidly prototype nonlocal metasurfaces that spatially shape thermal emission.

关键词： theory resonant spatially

Multifunctional resonant wavefront-shaping meta-optics based on multilayer and multi-perturbation nonlocal metasurfaces

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Light(Science & Applications) 2022年第9期11卷 2194-2206页

作者： STEPHANIE CMalEK ADAM COVERVIG andrea alù NANFANG YU Department of Applied Physics and Applied Mathematics Columbia UniversityNew YorkNY 10027USA Photonics Initiative Advanced Science Research CenterCity University of New YorkNew YorkNY 10031USA Physics Program Graduate CenterCity University of New YorkNew YorkNY 10016USA

Photonic devices rarely provide both elaborate spatial control and sharp spectral control over an incoming *** optical metasurfaces,for example,the localized modes of individual meta-units govern the wavefront shape over a broad bandwidth,while nonlocal lattice modes extended over many unit cells support high quality-factor ***,we experimentally demonstrate nonlocal dielectric metasurfaces in the near-infrared that offer both spatial and spectral control of light,realizing metalenses focusing light exclusively over a narrowband resonance while leaving off-resonant frequencies *** devices attain this functionality by supporting a quasi-bound state in the continuum encoded with a spatially varying geometric *** leverage this capability to experimentally realize a versatile platform for multispectral wavefront shaping where a stack of metasurfaces,each supporting multiple independently controlled quasi-bound states in the continuum,molds the optical wavefront distinctively at multiple wavelengths and yet stay transparent over the rest of the *** a platform is scalable to the visible for applications in augmented reality and transparent displays.

关键词： spectrum resonant supporting

Metasurfaces for next-generation wireless communication systems

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National Science Review 2023年第8期10卷 17-19页

作者： Younes Ra'di Nikita Nefedkin Petar Popovski andrea alù Department of Electrical Engineering and Computer Science Syracuse University Photonics Initiative Advanced Science Research Center City University of New York Department of Electronic Systems Aalborg University Physics Program Graduate Center City University of New York

The pace of development in the world of 5G communication systems has proven to be much more demanding than previous generations, with 5G-Advanced seemingly around the corner [1]. Extensive research is already underway to structure the next generation of wireless systems(i.e. 6G), which may potentially enable an unprecedented level of human–machine interaction [2].

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Microwave Tunneling and Robust Information Transfer Based on Parity-Time-Symmetric Absorber-Emitter Pairs

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Research 2019年第1期2019卷 105-114页

作者： Zhicheng Xiao Younes Ra’di Sergei Tretyakov andrea alù Department of Electrical and Computer Engineering The University of Texas at AustinAustinTX 78712USA Advanced Science Research Center City University of New YorkNew YorkNY 10031USA Department of Electronics and Nanoengineering Aalto UniversityFI-00076 AaltoFinland

Robust signal transfer in the form of electromagnetic waves is of fundamental importance in modern technology,yet its operation is often challenged by unwanted modifications of the channel connecting transmitter and ***-time-(PT-)symmetric systems,combining active and passive elements in a balanced form,provide an interesting route in this ***,we demonstrate a PT-symmetric microwave system operating in the extreme case in which the channel is shorted through a small reactance,which acts as a nearly impenetrable obstacle,and it is therefore expected to induce large reflections and poor *** placing a gain element behind the obstacle,and a balanced lossy element in front of it,we observe full restoration of information and overall transparency to an external observer,despite the presence of the *** theory,simulations,and experiments unambiguously demonstrate stable and robust wave tunneling and information transfer supported by PT symmetry,opening opportunities for efficient communication through channels with dynamic changes,active filtering,and active metamaterial technology.

关键词： obstacle Tunnel element

Floquet metamaterials

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eLight 2022年第1期2卷 99-111页

作者： Shixiong Yin Emanuele Galiffi andrea alù Photonics Initiative Advanced Science Research CenterThe City University of New York85 St.Nicholas TerraceNew York 10031USA Department of Electrical Engineering City CollegeThe City University of New York160 Convent AvenueNew York 10031USA Physics Program The Graduate CenterThe City University of New York365 Fifth AvenueNew York 10016USA

Recent progress in nanophotonics and material science has inspired a strong interest in optically-induced material dynamics,opening new research directions in the distinct fields of Floquet matter and time *** phenomena are historically rooted in the condensed matter community,as they exploit periodic temporal drives to unveil novel phases of matter,unavailable in systems at *** parallel,the field of metamaterials has been offering a platform for exotic wave phenomena based on tailored materials at the nanoscale,recently enhanced by incorporating time variations and switching as new degrees of *** this Perspective,we connect these research areas and describe the exciting opportunities emerging from their synergy,hinging on giant wave-matter interactions enabled by metamaterials and on the exotic wave dynamics enabled by Floquet and parametric *** envision Floquet metamaterials in which nontrivial modulation dynamics,and their interplay with tailored material dispersion and nontrivial material properties such as anisotropy,non-Hermiticity and nonreciprocity,introduce a plethora of novel opportunities for wave manipulation and control.

关键词： Floquet Metamaterials Time Switching

Wavefront-selective Fano resonant metasurfaces

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Advanced Photonics 2021年第2期3卷 78-88页

作者： Adam Overvig andrea alù City University of New York Advanced Science Research CenterPhotonics InitiativeNew YorkUnited States City University of New York Graduate CenterPhysics ProgramNew YorkUnited States

Fano resonances are conventionally understood as sharp spectral features with selectivity in the momentum-frequency domain,implying that they can be excited only by plane waves with specific frequencies and incident *** demonstrate that Fano resonances can be made generally selective in the spacefrequency *** can be tailored to resonate only when excited by a frequency,polarization,and wavefront of *** generalization reveals that Fano systems are characterized by eigenwaves that scatter to their time-reversed image upon *** in conventional Fano systems this trivially occurs for normally incident plane waves,we show that,in general,the selected wavefront is locally retroreflected everywhere across the *** results show that conventional Fano resonances are a subset of a broader dichroic phenomenon with spin,spatial,and spectral *** demonstrate these concepts with nonlocal metasurfaces whose governing principles are deeply rooted in the symmetry features of quasi-bound states in the *** light–matter interactions and symmetry-protection make these phenomena uniquely suited for enriching applications in quantum optics,non-linear optics,augmented reality,and secure optical communications,laying the groundwork for a range of novel compact optical sources and devices.

关键词： nonlocal metasurface Fano resonance spatial selectivity quasi-bound states in the continuum

Topological scattering singularities and embedded eigenstates for polarization control and sensing applications

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Photonics Research 2021年第7期9卷 1310-1323页

作者： ZARKO SAKOTIC alEX KRASNOK andrea alú NIKOLINA JANKOVIC BioSense Institute-Research Institute for Information Technologies in Biosystems University of Novi SadDr Zorana Djindjica 1a 21101Novi SadSerbia Advanced Science Research Center City University of New YorkNew York 10031USA Physics Program Graduate CenterCity University of New YorkNew York 10016USA

Epsilon-near-zero and epsilon near-pole materials enable reflective systems supporting a class of symmetryprotected and accidental embedded eigenstates (EEs) characterized by a diverging phase resonance. Here we show that pairs of topologically protected scattering singularities necessarily emerge from EEs when a non-Hermitian parameter is introduced,lifting the degeneracy between oppositely charged singularities. The underlying topological charges are characterized by an integer winding number and appear as phase vortices of the complex reflection coefficient. By creating and annihilating them,we show that these singularities obey charge conservation,and provide versatile control of amplitude,phase,and polarization in reflection,with potential applications for polarization control and sensing.

关键词： topological protected integer

Chiral transmission by an open evolution trajectory in a non-Hermitian system

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Light(Science & Applications) 2024年第4期13卷 628-636页

作者： Xiaoqian Shu Qi Zhong Kai Hong Oubo You Jian Wang Guangwei Hu andrea alù Shuang Zhang Demetrios N.Christodoulides Lin Chen Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information Huazhong University of Science and TechnologyWuhan 430074China. Zhejiang Lab Hangzhou 311121China. CREOL College of Optics and PhotonicsUniversity of Central FloridaOrlandoFlorida 32816USA. Department of Physics The University of Hong KongHong KongChina. School of Electrical and Electronic Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore. Photonics Initiative Advanced Science Research CenterCity University of New YorkNew YorkNY 10031USA. Shenzhen Huazhong University of Science and Technology Research Institute Shenzhen 518063China

Exceptional points(EPs),at which two or more eigenvalues and eigenstates of a resonant system coalesce,are associated with non-Hermitian Hamiltonians with gain and/or loss *** encircling of EPs has received significant interest in recent years,as it has been shown to lead to highly nontrivial phenomena,such as chiral transmission in which the final state of the system depends on the encircling ***,chiral transmission for a pair of eigenmodes has been realized by establishing a closed dynamical trajectory in parity-time-(PT-)or anti-PT-symmetric *** chiral transmission of symmetry-broken modes,more accessible in practical photonic integrated circuits,has been realized by establishing a closed trajectory encircling EPs in anti-PTsymmetric systems,the demonstrated transmission efficiency is very low due to path-dependent ***,we demonstrate chiral dynamics in a coupled waveguide system that does not require a closed ***,we explore an open trajectory linking two infinite points having the same asymptotic eigenmodes(not modes in PT-and anti-PT-symmetric systems),demonstrating that this platform enables high-efficiency chiral transmission,with each eigenmode localized in a single *** concept is experimentally implemented in a coupled silicon waveguide system at telecommunication *** work provides a new evolution strategy for chiral dynamics with superior performance,laying the foundation for the development of practical chiral-transmission devices.

关键词： chiral system symmetric

Topological photonics and beyond:introduction

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Photonics Research 2021年第1期9卷 I0001-I0002页

作者： andrea alù LAURA PILOZZI HAITAN XU JINGYUN FAN Photonics Initiative Advanced Science Research CenterCity University of New YorkNew York 10031USA Physics Program Graduate CenterCity University of New YorkNew YorkNew York 10016USA Institute for Complex Systems National Research Council(ISC-CNR)Via dei Taurini 1900185 RomeItaly Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and TechnologyShenzhen 518055China State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics School of PhysicsPeking UniversityBeijing 100871China

Topological photonics has been opening exciting opportunities in recent optics *** this feature issue,we present a collection of papers outlining state-of-the-art and application perspectives for this thriving field o... 详细信息

关键词： beyond optics photonics