All-optical Hall effect by the dynamic toroidal moment in a cavity-based metamaterial

Dong, Zheng‐Gao; Zhu, Jie; Yin, Xiaobo; Li, Jiaqi; Lü, Changgui; Zhang, Xiang

doi:10.1103/physrevb.87.245429

Cited by 72 publications

(80 citation statements)

References 42 publications

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“…Various metamaterial designs have already been utilized experimentally to promote a toroidal dipole response in the microwave and optical part of the spectrum: circular apertures in a metallic screen [18], asymmetric split rings [19], split rings [20,21], and double bars [22]. In numerical simulations, also other resonator configurations [23][24][25][26][27] have shown notable toroidal dipole responses.…”

Section: Introductionmentioning

confidence: 99%

Toroidal dipole excitations in metamolecules formed by interacting plasmonic nanorods

et al. 2016

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We show how the elusive toroidal dipole moment appears as a radiative excitation eigenmode in a metamolecule resonator that is formed by pairs of plasmonic nanorods. We analyze one such nanorod configuration-a toroidal metamolecule. We find that the radiative interactions in the toroidal metamolecule can be qualitatively represented by a theoretical model based on an electric point dipole arrangement. Both a finite-size rod model and the point dipole approximation demonstrate how the toroidal dipole moment is subradiant and difficult to excite by incident light. By means of breaking the geometric symmetry of the metamolecule, the toroidal mode can be excited by linearly polarized light and appears as a Fano resonance dip in the forward scattered light. We provide simple optimization protocols for maximizing the toroidal dipole mode excitation. This opens up possibilities for simplified control and driving of metamaterial arrays consisting of toroidal dipole unit-cell resonators.

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Section: Introductionmentioning

confidence: 99%

Toroidal dipole excitations in metamolecules formed by interacting plasmonic nanorods

et al. 2016

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“…Toroidal metamaterials [48][49][50][51][52][53][54] have been designed to maximize the toroidal dipole response, which is formed by a poloidal current on a torus surface and cannot be described in a standard multipole expansion [55,56] unlike electric multipoles and magnetic multipoles. Due to the unique features of toroidal dipoles such as strong EM energy confinement and weak coupling to free space [57], toroidal metamaterials are expected to have potential application in enhancing light-matter interactions.…”

Section: Introductionmentioning

confidence: 99%

Subwavelength localization and toroidal dipole moment of spoof surface plasmon polaritons

Kim

et al. 2015

Phys. Rev. B

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We experimentally and theoretically demonstrate subwavelength scale localization of spoof surface plasmon polaritons at a point defect in a two-dimensional groove metal array. An analytical expression for dispersion relation of spoof surface plasmon polaritons substantiates the existence of a band gap where a defect mode can be introduced. A waveguide coupling method allows us to excite localized spoof surface plasmon polariton modes and measure their resonance frequencies. Numerical calculations confirm that localized modes can have a very small modal volume and a high Q factor both of which are essential in enhancing light-matter interactions. Interestingly, we find that the localized spoof surface plasmon polariton has a significant toroidal dipole moment, which is responsible for the high Q factor, as well as an electric quadrupole moment. In addition, the dispersion properties of spoof surface plasmon polaritons are analyzed using a modal expansion method and numerical calculations.

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“…In parallel, fabrication difficulties were also overcome by introducing artificial patterns that are less challenging to manufacturing at the nanoscale, where split-ring resonators are replaced by pairs of bars 63 (Fig. 3d) and disks 64,65 , while still supporting toroidal excitation modes. In the optical part of the spectrum, a toroidal dipole response, although weakened due to high ohmic losses in metals, was found in even simpler systems, such as plasmonic core-shell nanoparticles 66 , and bas-relief patterns that support spoof plasmons, including periodic grids 67 and arrays of ring-shaped grooves illuminated at oblique angles 68 (Fig.…”

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Electromagnetic toroidal excitations in matter and free space

et al. 2016

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The toroidal dipole is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles. While the electric dipole can be understood as a pair of opposite charges and the magnetic dipole as a current loop, the toroidal dipole corresponds to currents flowing on the surface of a torus. Toroidal dipoles provide physically significant contributions to the basic characteristics of matter including absorption, dispersion, and optical activity. Toroidal excitations also exist in free-space as spatially and temporally localized electromagnetic pulses propagating at the speed of light and interacting with matter. We review recent experimental observations of resonant toroidal dipole excitations in metamaterials and the discovery of anapoles, non-radiating current configurations involving toroidal dipoles. While certain fundamental and practical aspects of toroidal electrodynamics remain open for the moment, we envision that exploitation of toroidal response can have important implications for the fields of photonics, sensing, energy and information. IntroductionThe interactions of electromagnetic radiation with matter underpin some of the most important technologies today -from telecommunications to information processing and data storage; from spectroscopy and imaging to light-assisted manufacturing. Our understanding and description of the electromagnetic properties of matter traditionally involves the concept of electric and magnetic dipoles, as well as their more complex combinations, known as multipoles. Introduced by Maxwell and Lorentz and later refined by Jackson and Landau, this framework, termed the multipole expansion, is central in physics and is being routinely applied in the study of optical, condensed matter, atomic, nuclear phenomena and beyond 1 . Within this framework, electromagnetic media can be represented by a set of point-like multipole sources [2][3][4][5] . The commonly used set of multipoles comprises the electric and magnetic families, which can be represented by oscillating charges and loop currents respectively. Dynamic toroidal multipoles constitute a third independent family of elementary electromagnetic sources, rather than an alternative multipole expansion or higher-order corrections to the conventional electric and magnetic multipoles (see tutorial inset I).Introduced in 1958 by Y. B. Zeldovich, toroidal moments have been considered in systems of toroidal topology (see Fig. 1) and studied in the context of nuclear 6 , atomic 7 , and molecular physics 8 , classical electrodynamics 9,10 , and solid state physics 3 . In the field of electromagnetism, in particular, a number of works have led to the development of a complete theoretical framework for toroidal electrodynamics [11][12][13][14][15] and the prediction of exotic effects, including dynamic non-radiating charge current configurations 10 and non-reciprocal interactions 9 . Following recent experimental observations of toroidal contributions in the response of materials across the electromagnetic spectrum, dyn...

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All-optical Hall effect by the dynamic toroidal moment in a cavity-based metamaterial

Cited by 72 publications

References 42 publications

Toroidal dipole excitations in metamolecules formed by interacting plasmonic nanorods

Toroidal dipole excitations in metamolecules formed by interacting plasmonic nanorods

Subwavelength localization and toroidal dipole moment of spoof surface plasmon polaritons

Electromagnetic toroidal excitations in matter and free space

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