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The review presents an analysis and generalization of classical and most modern approaches to the description and development of operation of open optical nanoresonators, that is, resonators all sizes of which are smaller than the resonant wavelength of radiation in a vacuum. Particular attention is paid to the physics of such phenomena as bound states in a continuum, anapole states, supercavity modes, and perfect nonradiating modes with extremely high quality factors and localizations of electromagnetic fields. An analysis of the optical properties of natural oscillations in nanoresonators made of metamaterials is also presented in the review. The effects considered in this review, besides being of fundamental import can also find applications in the development of optical nanoantennas, nanolasers, biosensors, photovoltaic devices, and nonlinear nanophotonics., Comment: 73 pages,31 figures

The existence of an infinite number of perfect nonradiating modes in elliptical nanofibers is demonstrated. Dispersion laws are found for TM and TE perfect modes in circular and elliptical waveguides with an arbitrary eccentricity. Numerical simulations in Comsol Multiphysics have shown that these modes can be excited by plane waves of a certain parity and have extremely low radiative losses and extremely high quality factors. The found modes can be used to create highly sensitive nanosensors and other optical nanodevices where radiation losses should be minimal., Comment: 33 pages, 16 figures,small misprints are fixed

A general concept of perfect nonradiating modes in dielectric nanoparticles of an arbitrary shape is put forward. It is proved that such modes exist in axisymmetric dielectric nanoparticles and have unlimited radiative Q-factors. With smart tuning of the excitation beams, perfect modes appear as deep minima in the scattered radiation spectra (up to complete disappearance), but at the same time, they have a giant amplification of the fields inside the particle. Such modes have no analogs and can be useful for the realization of nanosensors, low threshold nanolasers, and other strong nonlinear effects in nanoparticles., Comment: 27 pages, 13 figures

The most important direction in the development of fundamental and applied physics is the study of the properties of optical systems at the nanoscale in order to create optical and quantum computers, biosensors, single-photon sources for quantum informatics, devices for DNA sequencing, sensors of various fields, etc. In all these cases, nanoscale light sources - dye molecules, quantum dots (epitaxial or colloidal), color centers in crystals, and nanocontacts in metals - are of key importance. In the nanoenvironment, the characteristics of these elementary quantum systems - pumping rates, radiative and non-radiative decay rates, the local density of states, lifetimes, level shifts - experience changes that can be used intentionally to create nanoscale light sources with desired properties. This review presents an analysis of actual theoretical and experimental works in the field of elementary quantum systems radiation control using plasmonic and dielectric nanostructures, metamaterials, and nanoparticles made from metamaterials., Comment: 94 pages, 55 figures, review paper to appear in Physics-Uspekhi

In the diffraction of visible light by a dielectric microcylinder packages of evanescent waves always arise. However, a single-wave incidence corresponds to rather small impact of evanescent waves outside the cylinder. In this paper, we theoretically show that a symmetric pair of plane waves impinging a glass microcylinder corresponds to much higher impact of the evanescent waves. Namely, the interference of the evanescent waves with the propagating ones results in the suppression of the electromagnetic field in an area with very small cross section. This area is located in free space at a substantial distance from the {rear side of the microcylinder and along its axis}. It may serve a linear optical trap for cold atoms and ions.

The exact analytical solution of Maxwell equations for a Bessel light beam scattered by a sphere is found. Scattered power, stored energy and a generalized Q factor as a function of frequency, the sphere radius, permittivity, and the Bessel beam angle are found. On the base of this solution, modes and pseudo-modes of a dielectric sphere are extracted by calculation of the generalized Q factor. It is shown that an appropriate choice of Bessel beam parameters can provide excitation of a single given mode and an unlimited value of the radiative Q factor of pseudo-modes.

We have derived and investigated analytical expressions for the spontaneous emission radiative decay rate of an optically active (chiral) molecule placed near a chiral (bi-isotropic) triaxial nanoellipsoid, which size is much smaller than the wavelength. Differences in radiative decay rates of optically active molecule enantiomers located near the surface of chiral nanoparticles of spherical, prolate spheroidal, and ellipsoidal shapes have been investigated. It is shown that the change of the nanoparticle shape from spherical to ellipsoidal can lead to substantial enhancement of the spontaneous emission radiative decay rate of molecule enantiomers of one type in comparison with the decay rate of the other type of enantiomers., Comment: 19 pages,5 figures

We study the optical properties of bi-anisotropic optical waveguides with nontrivial topological structure in wavevector space, placed in an ordinary dielectric matrix. We derive an exact analytical description of the eigenmodes of the systems with arbitrary parameters that allows us to investigate topologically protected surface states (TPSS) in details. In particular, we find that the TPSS on the waveguides would disappear (1) if their radius is smaller than a critical radius due to the dimensional quantization of azimuthal wavenumber, and also (2) if the permittivity of the host-medium exceeds a critical value. Interestingly, we also find that the TPSS in the waveguides have negative refraction for some geometries. We have found a TPSS phase diagram that will pave the way for development of the topological waveguides for optical interconnects and devices., Comment: 21 pages, 16 figures

Optical properties of the photonic crystal covered with a perforated metal film were investigated and the existence of the Fano-type resonances was shown. The Fano resonances originate from the interaction between the optical Tamm state and the waveguide modes of the photonic crystal. It manifests itself as a narrow dip in a broad peak in the transmission spectrum related to the optical Tamm state. The design of a sensor based on this Fano resonance that is sensitive to the change of the environment refractive index is suggested.

We have investigated the spontaneous decay rate of an excited molecule placed near a circular aperture in a metal film of finite thickness and finite conductivity. We have considered the metal film both suspended freely in vacuum and lying on a substrate. A significant effect of molecule the position and the presence of the substrate on the rate of spontaneous emission of the molecule is shown. The asymptotes which can be used to describe this process are found. Total, radiative, and non-radiative spontaneous decay rates of the excited molecule are extracted and compared. The results may be useful in the development and interpretation of experiments investigating a single molecule with a scanning optical microscope and in the design of optical nanodevices based on the control of elementary quantum systems emission with a nanohole.

The eigenoscillations in a two-dimensional dimer made of gain and lossy nanoparticles were investigated within exact analytical approach. It was shown that there are eigenoscillations for which all Joule losses are exactly compensated by the gain. Among such solutions, there are solutions with a new type of symmetry, which we refer to as Loss Compensation Symmetry (LCS) as well as well-known PT (parity-time) symmetric solutions. The modes with LCS unlike PT symmetric ones allow one to achieve full loss compensation with significantly less gain that in the case of PT symmetry. This effect paves way to the new loss compensation methods in optics., Comment: 10 pages, 6 figures

Artificial thin glass opals can be infiltrated with a resonant alkali-metal vapour, providing novel types of hybrid systems. The reflection at the interface between the substrate and the opal yields a resonant signal, which exhibits sub-Doppler structures in linear spectroscopy for a range of oblique incidences. This result is suspected to originate in an effect of the three-dimensional confinement of the vapour in the opal interstices. It is here extended to a situation where the opal is limited to a few or even a single layer opal film, which is a kind of bidimensional grating. We have developed a flexible one-dimensional layered optical model, well suited for a Langmuir-Blodgett opal. Once extended to the case of a resonant infiltration, the model reproduces quick variations of the lineshape with incidence angle or polarization. Alternately, for an opal limited to a single layer of identical spheres, a three-dimensional numerical calculation was developed. It predicts crystalline anisotropy, which is demonstrated through diffraction on an empty opal made of a single-layer of polystyrene spheres., Comment: to appear in Europhysics Letters, Special Issue (Proceedings of META 14-Singapore May 2014)

We investigate the light transmission through a nanoaperture in a metal film deposited on a planar metamaterial. An effect of an anomalously high light transmission through the nanoaperture is revealed, which we associate with the enhancement of the field at the interface of the planar structure "metamaterial-metal" due to the appearance of an optical Tamm state. In this structure, we also observe an "optical diode" effect: the light transmission radically changes as the direction of irradiation of the structure is reversed. Our numerical results agree well with experimental data., Comment: 17 pages, 8 figures

We propose to use double negative (DNG) metamaterial slabs to build effective super-absorbers and perfect nanodetectors for single divergent sources. We demonstrate by numerical simulations that an absorbing nanoparticle properly placed inside a DNG slab back-covered with a perfect electric conductor or perfect magnetic conductor mirror can absorb up to 100% radiation energy of a single dipole source placed outside the slab. Furthermore, we also show that even the simple DNG slab without any absorbing nanoparticle could be used as a perfect absorber for both plane and divergent beams. The proposed systems may focus the radiation in nanoscale and thus have applications in optical nanodevices for a variety of different purposes., Comment: Accepted for publication in Optics Express

We show that propagating optical fields bearing an axial symmetry are not truly hollow in spite of a null electric field on-axis. The result, obtained by general arguments based upon the vectorial nature of electromagnetic fields, is of particular significance in the situation of an extreme focusing, when the paraxial approximation no longer holds. The rapid spatial variations of fields with a "complicated" spatial structure are extensively analyzed in the general case and for a Laguerre-Gauss beam 2 as well, notably for beams bearing a |l| = 2 orbital angular momentum for which a magnetic field and a gradient of the electric field are present on-axis. We thus analyze the behavior of a atomic size light-detector, sensitive as well to quadrupole electric transitions and to magnetic dipole transitions, and apply it to the case of Laguerre-Gauss beam. We detail how the mapping of such a beam depends on the nature and on the specific orientation of the detector. We show also that the interplay of mixing of polarization and topological charge, respectively associated to spin and orbital momentum when the paraxial approximation holds, modifies the apparent size of the beam in the focal plane. This even leads to a breaking of the cylindrical symmetry in the case of a linearly polarized transverse electric field., Comment: accepted for publication (april 18, 2012) in Physicial Review A

In the framework of the perturbation theory of the nonrelativistic quantum electrodynamics, a theory of spontaneous emission of a chiral molecule located near a chiral (bi-isotropic) spherical particle is developed. It is shown that the structure of photons in the presence of chiral spherical particles differs significantly from the structure of TE or TM photons. Exact analytical expressions for the spontaneous emission radiative decay rate of a chiral molecule with arbitrary electric and magnetic dipole moments of transition located near a chiral spherical particle with arbitrary parameters are obtained and analyzed in details. Simple asymptotes for the case of a nanoparticle are obtained. Substantial influence of even small chirality on a dielectric or "left-handed" sphere is found. It is shown that by using chiral spherical particles it is possible to control effectively the radiation of enantiomers of optically active molecules., Comment: 29 pages, 6 figures

Based on both analytical dipole model analyses and numerical simulations, we propose a concept of coherent perfect nanoabsorbers (CPNAs) for divergent beams. This concept makes use of the properties of a slab with negative refraction and small losses. The proposed CPNA device would allow focusing radiation in nanoscale regions, and hence could be applied in optical nanodevices for such diverse purposes as reading the results of quantum computation which is based on single photon qubits., Comment: 11 pages 9 figures

The radiation of optically active (chiral) molecule placed near chiral nanoparticle is investigated. The optimal conditions for engineering of radiation of optically active (chiral) molecules with the help of chiral nanoparticles are derived. It is shown that for this purpose, the substance of the chiral particle must have both \epsilon_and \mu_negative (double negative material (DNG)) or negative \mu_and positive \epsilon_(\mu_negative material (MNG)). Our results pave the way to an effective engineering of radiation of "left" and "right" molecules and to creating pure optical devices for separation of drugs enantiomers., Comment: 6 pages 6 figures