Radiation of Dynamic Toroidal Moments

Guo, Surong; Talebi, Nahid; Campos, Alfredo; Kociak, Mathieu; Aken, Peter A. van

doi:10.1021/acsphotonics.8b01422

Cited by 23 publications

(16 citation statements)

References 44 publications

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“…However, the use of structured light, most notably space-time non-separable pulses with toroidal topology may help, as they are better suited to drive toroidal excitations than transverse pulses 59 . Alternatively, toroidal and electric dipole constituents of an anapole mode could be engaged with electron beam excitations 60 .…”

Section: Detection Of Anapolesmentioning

confidence: 99%

Optical anapoles

et al. 2019

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The anapole, a non-radiating charge-current configuration, was recently observed in a variety of artificial materials and nanostructures. We provide a brief overview of this rapidly developing field and discuss implications for spectroscopy, energy materials, electromagnetics, as well as quantum and nonlinear optics. Toroidal electrodynamics, a new chapter of electromagnetics research is currently attracting considerable and growing attention 1-4. It includes the study of toroidal multipoles and anapoles (see Fig. 1). The recent surge of interest in toroidal multipoles is driven by the emerging understanding that alongside the well-known electric and magnetic multipoles they are necessary for a complete characterization of the electromagnetic properties of matter 2. Indeed, while electromagnetic fields in free-space can be fully characterized with transverse electric (TE) and transverse magnetic (TM) multipoles 5 , the characterization of current density requires three multipole series, the electric, magnetic, and toroidal multipoles 6,7 (see Fig. 2). The distinctive role of toroidal multipoles is particularly apparent in the optical properties of matter containing large molecules or structural elements of toroidal symmetry and of size comparable to the electromagnetic wavelength. Dynamic toroidal response of metamaterials had been the subject of intense discussions since 2007 8,9 , but the first unambiguous experimental demonstration of dominant toroidal response in matter was recorded in a microwave metamaterial in 2010 1 (see Fig. 3). Subsequently, dynamic toroidal response has been observed in metallic 10-15 , plasmonic 16-22 , and dielectric metamaterials 23,24 at frequencies ranging from microwave through to terahertz and up to near-infrared/visible parts of the spectrum (see Fig. 3). The analysis of transmission, reflection 12 , and polarization phenomena 13 in complex molecular systems and metamaterials is incomplete without account of the dynamic toroidal response. Toroidal resonances could play a role in nano-lasers 19 , sensors 25 , and data storage devices 3,26. We shall also note that static toroidal dipoles, also known as 'static anapoles' introduced by Ya. B. Zeldovich in the context of parity violation in nuclear physics 27 , have been observed in magnetism 26 and could be the only allowed electromagnetic form-factor for dark matter candidate particles 28. An electric dipole (a pair of oscillating charges) together with a toroidal dipole (oscillating poloidal current on a torus (see Fig. 1)) can form a non-radiating charge-current configuration,

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Section: Detection Of Anapolesmentioning

confidence: 99%

Optical anapoles

et al. 2019

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“…[1][2][3][4][5] This integration can be attained by considering the data processing and waveguiding characteristics at more basic level, and the only possible way of overcoming those challenges is employing the concepts of metamaterials and metadevices based on structuring artificial matter at the subwavelength scales. [6][7][8] Optical magnetism, [9][10][11] asymmetric transmission, [12][13][14] hyperbolic dispersion, [15][16][17][18] epsilon near-zero (ENZ), [19][20][21][22] topological states, [23][24][25][26][27] arbitrary control of light's trajectories and cloaking, [28,29] excitation of toroidal fields and charge-current configurations, [30][31][32][33] and generation of flying doughnuts [34,35] are some of the fundamental discoveries that are allowed by metamaterials.…”

Section: Introductionmentioning

confidence: 99%

“…In relation to these exploration activities, in 2007, novel optical metamaterials based on the third family of electromagnetic multipoles, toroidal multipoles, were introduced by Marinov et al [48] Originally explored by Zel'dovich in 1957, [49] the toroidal phenomenon has been elucidated by virtue of various principles of physics. [32,33,[50][51][52] In the modern electromagnetic limit, primarily, the dynamic toroidal dipoles have been observed in 3D metamolecules across the microwave regime. [30] Toroidal resonant systems are well-known for producing unconventional gyrotropic-fashioned charge-current excitations' fingerprints with hidden far-field radiation.…”

Section: Introductionmentioning

confidence: 99%

“…[53] While there have been extensive studies to develop subwavelength systems capable of multipolar toroidal moments [54] and high-order multiloop supertoroidal currents, [55,56] of particular interest is the dynamic toroidal dipole that can be optically driven and recognized as a ring-shaped head-to-tail configuration of magnetic dipoles, intensely squeezed within a tiny spot. [30][31][32][33][34][35][55][56][57][58][59][60][61][62] Theoretically, the dynamic toroidal dipole offers physically substantial nonzero contributions to both the fundamental properties of matter and scattered radiation. [63,64] Up to now, dynamic toroidal charge-current configurations with different qualities have been excited in both planar (2D) and 3D architectures, as well as cavity oligomers from visible to IR, terahertz (THz), and microwave frequencies.…”

Section: Introductionmentioning

confidence: 99%

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Toroidal Metaphotonics and Metadevices

Ahmadivand

Gerislioglu

Ahuja

et al. 2020

Laser & Photonics Reviews

113

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Toroidal moments in artificial media have received growing attention and considered as a promising framework for initiating novel approaches to manage intrinsic radiative losses in nanophotonic and plasmonic systems. In the past decade, there has been substantial attention on the characteristics and excitation methods of toroidal multipoles-in particular, toroidal dipole-in 3D bulk and planar metaplatforms. The remarkable advantages of toroidal resonances have thrust the toroidal metasurface technology from relative anonymity into the limelight, in which researchers have recently centered on developing applied optical and optoelectronic subwavelength devices based on toroidal metaphotonics and metaplasmonics. In this focused contribution, the key principles of 3D and flatland toroidal metastructures are described, and the revolutionary tools that have been implemented based on this topology are briefly highlighted. Infrared photodetectors, immunobiosensors, ultraviolet beam sources, waveguides, and functional modulators are some of the fundamental and latest examples of toroidal metadevices that have been introduced and studied experimentally so far. The possibility of the realization of strong plexciton dynamics and pronounced vacuum Rabi oscillations in toroidal plasmonic metasurfaces are also presented in this review. Ultimate efficient extreme-subwavelength scale devices, such as low-threshold lasers and ultrafast switches, are thus in prospect.

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“…While EELS probes the primary excitations, the radiative damping during the relaxation process can be measured by cathodoluminescence (CL) spectroscopy [48,55,56]. Especially, the combined study of an object by EELS and CL gives complementary insight into its physical properties [57][58][59][60][61]. However, numerical calculations are essential to interpret experimental results and to understand the physics behind them.…”

Section: Introductionmentioning

confidence: 99%

Probing plasmonic excitation mechanisms and far-field radiation of single-crystalline gold tapers with electrons

Lingstädt

Talebi

Guo

et al. 2020

Phil. Trans. R. Soc. A.

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Conical metallic tapers represent an intriguing subclass of metallic nanostructures, as their plasmonic properties show interesting characteristics in strong correlation to their geometrical properties. This is important for possible applications such as in the field of scanning optical microscopy, as favourable plasmonic resonance behaviour can be tailored by optimizing structural parameters like surface roughness or opening angle. Here, we review our recent studies, where single-crystalline gold tapers were investigated experimentally by means of electron energy-loss and cathodoluminescence spectroscopy techniques inside electron microscopes, supported by theoretical finite-difference time-domain calculations. Through the study of tapers with various opening angles, the underlying resonance mechanisms are discussed. This article is part of a discussion meeting issue ‘Dynamic in situ microscopy relating structure and function’.

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Radiation of Dynamic Toroidal Moments

Cited by 23 publications

References 44 publications

Optical anapoles

Optical anapoles

Toroidal Metaphotonics and Metadevices

Probing plasmonic excitation mechanisms and far-field radiation of single-crystalline gold tapers with electrons

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