The study of resonant dielectric nanostructures with high refractive index is a new research direction in nanoscale optics and metamaterial-inspired nanophotonics. Because of the unique opticallyinduced electric and magnetic Mie resonances, high-index nanoscale structures are expected to complement or even replace different plasmonic components in a range of potential applications. Here we study strong coupling between modes of a single subwavelength high-index dielectric resonator and analyse the mode transformation and Fano resonances when resonator's aspect ratio varies. We demonstrate that strong mode coupling results in resonances with high quality factors, which are related to the physics of bound states in the continuum when the radiative losses are almost suppressed due to the Friedrich-Wintgen scenario of destructive interference. We explain the physics of these states in terms of multipole decomposition and show that their appearance is accompanied by drastic change of the far-field radiation pattern. We reveal a fundamental link between the formation of the high-quality resonances and peculiarities of the Fano parameter in the scattering cross-section spectra. Our theoretical findings are confirmed by microwave experiments for the scattering of a high-index cylindrical resonators with a tunable aspect ratio. The proposed mechanism of the strong mode coupling in single subwavelength high-index resonators accompanied by resonances with high quality factor helps to extend substantially functionalities of all-dielectric nanophotonics that opens new horizons for active and passive nanoscale metadevices. arXiv:1805.09265v2 [physics.optics] 1 Dec 2018

The routing of light in a deep subwavelength regime enables a variety of important applications in photonics, quantum information technologies, imaging and biosensing. Here we describe and experimentally demonstrate the selective excitation of spatially confined, subwavelength electromagnetic modes in anisotropic metamaterials with hyperbolic dispersion. A localized, circularly polarized emitter placed at the boundary of a hyperbolic metamaterial is shown to excite extraordinary waves propagating in a prescribed direction controlled by the polarization handedness. Thus, a metamaterial slab acts as an extremely broadband, nearly ideal polarization beam splitter for circularly polarized light. We perform a proof of concept experiment with a uniaxial hyperbolic metamaterial at radio-frequencies revealing the directional routing effect and strong subwavelength l/300 confinement. The proposed concept of metamaterial-based subwavelength interconnection and polarizationcontrolled signal routing is based on the photonic spin Hall effect and may serve as an ultimate platform for either conventional or quantum electromagnetic signal processing.

Resonant slot nanoantennas for surface plasmon radiation in optical frequency range Appl. Phys. Lett. 100, 241115 (2012); 10.1063/1.4729552Experimental realization of all-dielectric composite cubes/rods left-handed metamaterial

We demonstrate that spectrally diverse multiple magnetic dipole resonances can be excited in all-dielectric structures lacking rotational symmetry, in contrast to conventionally used spheres, disks or spheroids. Such multiple magnetic resonances arise from hybrid Mie-Fabry-Pérot modes, and can constructively interfere with induced electric dipole moments, thereby leading to novel multi-frequency unidirectional scattering. Here we focus on elongated dielectric nanobars, whose magnetic resonances can be spectrally tuned by their aspect ratios. Based on our theoretical results, we suggest all-dielectric multimode metasurfaces and verify them in proof-ofprinciple microwave experiments. We also believe that the demonstrated property of multimode directionality is largely responsible for the best efficiency of all-dielectric metasurfaces that were recently shown to operate across multiple telecom bands.

All-dielectric resonant nanophotonics lies at the heart of modern optics and nanotechnology due to the unique possibilities to control scattering of light from high-index dielectric nanoparticles and metasurfaces. One of the important concepts of dielectric Mie-resonant nanophotonics is associated with the Kerker effect that drives the unidirectional scattering of light from nanoantennas and Huygens' metasurfaces. Here we suggest and demonstrate experimentally a novel effect manifested in the nearly complete simultaneous suppression of both forward and backward scattered fields. This effect is governed by the Fano interference between an electric dipole and off-resonant quadrupoles, providing necessary phases and amplitudes of the scattered fields to achieve the transverse scattering. We extend this concept to dielectric metasurfaces that demonstrate zero reflection with transverse scattering and strong field enhancement for resonant light filtering, nonlinear effects, and sensing.

We suggest and verify experimentally the concept of functional metamaterials whose properties are remotely controlled by illuminating the metamaterial with a pattern of visible light. In such metamaterials arbitrary gradients of the effective material parameters can be achieved simply by adjusting the profile of illumination. We fabricate such light-tunable microwave metamaterials and demonstrate their unique functionalities for reflection, shaping, and focusing of electromagnetic waves.

Since the beginning of the 20th century, researchers have been looking for an effective way to transfer power without wired connections, but the wireless power transfer technology started to attract extensive interest from the industry side only in 2007 when the first smartphone was released and a consumer electronics revolution was triggered. Currently, the modern technology of wireless power transfer already has a rich research and development history as well as outstanding advances in commercialization. This review is focused on the description of distinctive implementations of this technology inspired by the modern trends in electrodynamics. We compare the performances of the power transfer systems based on three kinds of resonators, i.e., metallic coil resonators, dielectric resonators, and cavity mode resonators. We argue that metamaterials and meta-atoms are powerful tools to improve the functionalities and to obtain novel properties of the systems. We review different approaches to enhance the functionality of the wireless power transfer systems including control of the power transfer path and increase of the operation range and efficiency. Various applications of wireless power transfer are discussed and currently available standards are reviewed.

helix (a solenoid) bent in a ring (a toroid). The current flowing through the helix cre ates a magnetic field trapped inside the toroid. The resulting moment of such a system is oriented along the axis of revo lution of the toroid, and it is defined as a toroidal moment. If the toroid is rigid, then no magnetic field produced by external sources can act on the toroid as a whole. In the nonideal case, an electro magnetic coupling with such a toroidal moment is possible, although one can expect that this effect should be very weak and hardly measurable. Despite this, the toroidal moment was found to exist in different problems of condensed matter physics, and it was studied in many papers. [2][3][4][5] Similar to the standard multipole expansion [6] related to the electromag netic potentials and sources, the toroidal multipoles originated from the decompo sition of the moment tensor have a dual nature. [7] It means that there appears a distinction between magnetic and electric toroidal multipoles manifested in different flow paths of their polarization cur rents. In particular, a magnetic (polar) toroidal dipole is created by the polarization currents flowing on a surface of a toroid along its meridian (the poloidal direction), whereas an electric (axial) toroidal dipole appears from a ring of polarization cur rents flowing along the toroid (the toroidal direction).The study of toroidal dipole modes has attracted a growing attention due to the specific properties of the toroidal electromagnetic response which differs from more familiar electric and magnetic dipole modes. Herein, toroidal dipole modes generated by metasurfaces composed of trimer clusters of high-index dielectric particles are observed. Both far-field transmission measurements and direct near-field mapping of the electromagnetic fields are performed in microwave experiments, and two distinct types of the toroidal dipole modes are observed in a single geometry of the metasurface design, where the toroidal modes are generated either inside of the three- particle clusters (the so-called intra-cluster toroidal modes) or between the neighboring particles in the clusters (inter-cluster toroidal modes). A transient response of the toroidal dipole modes excited by a pulse is studied in detail.Since the metasurface is composed of simple dielectric disks without the use of any metallic components, the proposed design can be feasibly scalable to both micro-and nanometer-size dielectric structures, and it can be employed in the flat-optics platform for realizing the beams shaping and efficient light-matter interaction for multiple hotspot energy localization, nonlinear frequency conversion, and highly efficient trapping of light. Toroidal Dipole ModesAppearance of a toroidal moment is an intriguing phenomenon in the physics of light-matter interaction, first predicted theo retically in the middle of the last century. It was introduced in the particle physics in the study of the interaction with parity violation for elementary particles and weak electromagnetic f...