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Focused laser beams allow controlling the mechanical motion of objects and can serve as a tool for assembling micro and nanostructures in space. While small particles mainly experience attractive gradient forces and repulsive radiation pressure, introducing additional flexibility suggests approaching new capabilities. Herein, optical forces acting on a high refractive index sphere in a focused Gaussian beam are analyzed and new regimes are revealed. Multipolar analysis allows separating an optical force into interception and recoil components, resulting in different mechanical actions. In particular, interplaying interception radial forces and multipolar resonances within a particle can lead to either trapping or antitrapping, depending on the system parameters. At the same time, the recoil force generates a significant azimuthal component along with an angulardependent radial force. Those contributions enable enhancing either trapping or antitrapping and also introduce bending reactions. These effects are linked to the far-field multipole interference and, specifically, to asymmetric scattering patterns. The latter approach is extremely useful, as it allows assessing the nature of optomechanical motion by observing far-fields. Multipolar engineering of optical forces, being quite a general approach, is not necessarily linked to simple spherical shapes and paves a way to new possibilities in microfluidic applications, including sorting and microassembly

Bound states in the continuum (BIC) attracted great attention in the photonics community. The existence of such states has led to numerous applications, including optical sensors and filters. Here we report on the approach to externally tune a magnitude and spectral position of high-Q resonances, associated with not symmetry-protected BIC state in silicon nitride (Si3N4) photonic crystals. We show that BIC properties can be controlled by the external thermal impact. These results can be used to construct compact and thermally stable optical sensors immune to harsh environmental conditions.

A recently introduced femtosecond laser printing technique was further developed for the fabrication of crystalline single Ge and SiGe nanoparticles (NPs). Amorphous Ge and SiGe thin films deposited by e-beam evaporation on a transparent substrate were used as donors. The developed approach is based on a laser-induced forward transfer process, which provides an opportunity for NP-controlled positioning on different types of receiver substrates. The size of the generated nanoparticles can be varied from about 100 to 300 nm depending on the laser pulse energy and wavelength. The crystallinity and composition of nanoparticles are both confirmed by the Raman spectroscopy measurements. The experimental visible scattering spectra of single nanoparticles are found to be well coincident with theoretical simulations performed on the basis of Mie theory. It is demonstrated that Ge and SiGe nanoparticles are characterized by electric and magnetic dipole resonances in the visible and near-infrared spectral ranges, wh...

Structured environment controls dynamics of light-matter interaction processes via modified local density of electromagnetic states. In typical scenarios, where nanosecond-scale fluorescent processes are involved, mechanical conformational changes of the environment during the interaction processes can be safely neglected. However, slow decaying phosphorescent complexes (e.g. lanthanides) can efficiently probe micro- and millisecond scale motion via near-field interactions with nearby structures. As the result, lifetime statistics can inherit information about nano-scale mechanical motion. Here we study light-matter interaction dynamics of phosphorescent dyes, diffusing in a proximity of a plasmonic nanoantenna. The interplay between time-varying Purcell enhancement and stochastic motion of molecules is considered via a modified diffusion equation, and collective decay phenomena is analyzed. Fluid properties, such as local temperature and diffusivity, are mapped on phosphorescent lifetime distribution and then extracted with the help of inverse Laplace transformation. The presented photonic platform enables performing contactless all-optical thermometry and diffusion measurements, paving a way for a range of possible applications. In particular, detailed studies of nanofluidic processes in lab-on-a-chip devices, challenging for analysis with other optical methods, can be performed with time-dependent phosphorescence.

Nanoparticles made from dielectric materials with a high refractive index have caused a surge of interest and have been proposed for various all-dielectric nanophotonic applications. In this regard, the development of optical manipulation technology for such nanoparticles becomes an important task. High-index nanoparticles support electric and magnetic multipole responses in the visible wavelength range, and interference between such modes can manifest itself in optical forces. Here, we present a study of the optical forces acting on silicon nanoparticles in a Gaussian beam, calculated analytically using the Mie theory, as well as the numerical simulations results based on the Maxwell stress tensor. We have shown that the interaction of а laser beam electromagnetic field with electric and magnetic dipoles in a nanoparticle can lead to a possible anti-trapping effect. This behavior of the particle is not typical for optical tweezers, where the particle is usually attracted to the beam axis.

In this work, using the numerical simulation in the COMSOL Multiphysic package, we studied the optical properties of the hybrid anapole state in silicon nanocylinders and their metasurfaces. Our investigations show the possibility of creating invisible metasurfaces consisting of silicon cylinders based on the novel state. These results can be used in various fields of nanophotonics and may have important outcome in the development of various sensors and other photonic devices.

Here we study light-induced interaction of several dielectric particles above a hyperbolic metamaterial. It is shown, that both surface and volumetric modes of the substrate define distances between interacting particles, beyond the diffraction limit. Moreover, by varying the thickness of the metamaterial substrate it is possible to tune magnitude of the optical force and distances between the particles.

Optomechanics is a promising technique for a wide range of applications and an intensively studied branch of nanophotonics. The flexibility of optical manipulation can be increased with the help of auxiliary substrates providing additional degrees of freedom. In this paper, we consider optical force acting on a particle near a one-dimensional photonic crystal. The excitation of bulk and surface modes of the crystal occurs due to the near fields of the particle and does not require additional mechanisms. Oblique incidence of a plane wave can lead to the directional excitation of the substrate modes, and therefore, an optical pulling force arises.

In this work we considered lateral optical forces acting on high refractive index nanoparticles. It is shown that the tightly focused Gaussian beam exerts pulling or pushing forces on a spherical nanoparticle depending on the type and the order of an excited multipole resonance. The nanoparticle's refractive index thermal nonlinearity is used to demonstrate switching between multipole resonances and as a consequence the lateral force pushing/pulling regimes.

Structured environment controls dynamics of light-matter interaction processes via modified local density of electromagnetic states. In typical scenarios, where nanosecond-scale fluorescent processes are involved, mechanical conformational changes of the environment during the interaction processes can be safely neglected. However, slow decaying phosphorescent complexes (e.g. lanthanides) can efficiently sense micro- and millisecond scale motion via near-field interactions. As the result, lifetime statistics can inherit information about nano-scale mechanical motion. Here we study light-matter interaction dynamics of phosphorescent dyes, diffusing in a proximity of a plasmonic nanoantenna. The interplay between the time-varying Purcell enhancement and stochastic motion of molecules is considered via a modified diffusion equation, and collective decay phenomena is analysed. Fluid properties, such as local temperature and diffusion coefficient are mapped on phosphorescent lifetime distribution extracted with the help of inverse Laplace transform. We present rather simple photonic platform enabling contactless all-optical thermometry and diffusion measurement and paving a way for a plethora of possible applications. Among them, the proposed analysis can be used for detailed studies of nanofluidic processes in lab-on-a-chip devices, which are extremely hard or even impossible to analyse with other optical methods., 12 pages, 4 figures

We reveal that the Maxwell Garnett approximation is not capable of predicting a PT symmetry breaking in multilayers and a nonlocal homogenization theory should be employed. Interaction of electromagnetic beams consisting of plane and evanescent partial waves with the PT-symmetric systems is also studied.

Dielectric metasurfaces allow us to realize many unique effects in optics, and they can serve as the building blocks of the modern photonic technologies. Here, we suggest theoretically and demonstrate experimentally the effect of high transparency of all-dielectric metasurfaces with meta-atoms supporting the so-called transverse Kerker effect. In contrast to the well-known Huygens' metasurfaces, in our case both phase and amplitude of the incoming wave remain unperturbed at the resonant frequency and, consequently, our novel metasurfaces totally operate in the high-transparency regime. We prove experimentally, in the microwave frequency range, that both phase and amplitude of the waves transmitted through these metasurfaces remain almost unaffected. Also, we demonstrate numerically and experimentally and explain theoretically a novel mechanism for achieving a perfect absorption of the incident light enabled by the resonant response of the dielectric metasurfaces placed on a conducting substrate. In the subdiffractive limit, we show that these effects are mainly determined by the optical response of the constituting meta-atoms rather than collective lattice contributions. With the spectrum scalability, our finding can be extended to the optical frequencies to be employed for energy harvesting, nonlinear phenomena, and filtering of light.

Light scattering by all-dielectric nanoparticles attract significant attention of photonics community. Single nanoparticles can be used both as nanoantennas and as building blocks to construct 2D and 3D meta-structures. In this work we study scattering effect when silicon nanoparticles are embedded in different media. To analyze the evolution of multipole moments and their contributions to the scattering cross-sections of the nanoparticles in media, we use semi-analytical multipole decomposition approach. Explicitly, we investigate the behavior of electric and magnetic multipoles, up to third order, while dielectric nanoparticle made of silicon is embedded in a media. We found that electric and magnetic multipoles experience different red shift as refractive index increases. Due to this behavior separated high-order multipole resonances overlap with each other; thereby, scattering cross section peaks, which could be observed when a particles are in air, merge to the joint scattering cross section peaks. Such resonances overlap also affect both far-field radiation diagrams and field distribution inside the nanoparticle. Importantly, we noticed that when index of a surrounding media increases, the cubical nanoparticles provide spectral broadening of forward scattering effect. Our results provide fundamental information for understanding the scattering effect in all-dielectric nanoantennas or metasurfaces embedded in different dielectric media and operating in wide spectral range. For practical utilization, explored here dielectric nanoparticles could be used in broad range of applications such as in-vitro and in-vivo biomedical devices for sensing and drug delivering, sub-wavelength nano-amplifiers, and many other emerging applications.

Tuning the near field using all-dielectric nano-antennas offers a promising approach for trapping atoms, which could enable strong single-atom–photon coupling. Here we report the numerical study of an optical trapping of a single Cs atom above a waveguide with a silicon nano-antenna, which produces a trapping potential for atoms in a chip-scale configuration. Using counter-propagating incident fields, bichromatically detuned from the atomic cesium D-lines, we numerically investigate the dependence of the optical potential on the nano-antenna geometry. We tailor the near-field potential landscape by tuning the evanescent field of the waveguide using a toroidal nano-antenna, a configuration that enables trapping of ultracold Cs atoms. Our research opens up a plethora of trapping atoms applications in a chip-scale manner, from quantum computing to quantum sensing, among others.

We experimentally realize nano-antennas based on hybrid silicon-gold nanoparticles (NPs). The silicon particles covered by clusters of small metal NPs are fabricated from a liquid phase under the effect of the laser irradiation. The complex nanoclusters containing both Si and Au components provide the enhancement of the near-field intensity and the resonant light scattering associated with excitation of multipole resonances in NPs. A strong sensitivity of the resonant light absorption to the hybrid particle size and material parameters is experimentally documented and theoretically discussed. The results demonstrate a high potentiality of the hybrid NPs for the realization of functional optical devices and metasurfaces.

The optical force acting on a nanoparticle near a planar substrate is governed by incident light and excitation of surface and volume modes of the substrate. The realization of negative optical forces (“tractor beams”) via propagating plasmon-polaritones and volume modes will be shown and considered in detail on the basis of the described analytical and numerical models for certain types of anisotropic substrates. In addition, optical tweezers performance is investigated when the Gaussian beam is focused on the metal substrate with nanoparticle. When the beam is focused above the substrate optical force increases about an order of magnitude due to evanescent field of surface plasmon. Novel effect of repulsion from Gaussian beam (“anti-trapping”) is obtained when the beam waist is moved below the substrate which is confirmed by both the analytical approach and finite element simulation.The optical force acting on a nanoparticle near a planar substrate is governed by incident light and excitation of surface and volume modes of the substrate. The realization of negative optical forces (“tractor beams”) via propagating plasmon-polaritones and volume modes will be shown and considered in detail on the basis of the described analytical and numerical models for certain types of anisotropic substrates. In addition, optical tweezers performance is investigated when the Gaussian beam is focused on the metal substrate with nanoparticle. When the beam is focused above the substrate optical force increases about an order of magnitude due to evanescent field of surface plasmon. Novel effect of repulsion from Gaussian beam (“anti-trapping”) is obtained when the beam waist is moved below the substrate which is confirmed by both the analytical approach and finite element simulation.

[EN] Optical binding allows creation of mechanically stable nanoparticle configurations owing to formation of self-consistent optical trapping potentials. While the classical diffraction limit prevents achieving deeply subwavelength arrangements, auxiliary nanostructures enable tailoring optical forces via additional interaction channels. Here, a dimer configuration next to a metal surface was analyzed in detail and the contribution of surface plasmon polariton waves was found to govern the interaction dynamics. It is shown that the interaction channel, mediated by resonant surface waves, enables achieving subwavelength stable dimers. Furthermore, the vectorial structure of surface modes allows binding between two dipole nanoparticles along the direction of their dipole moments, contrary to vacuum binding, where a stable configuration is formed in the direction perpendicular to the polarization of the dipole moments. In addition, the enhancement by one order of magnitude of the optical binding stiffness is predicted owing to the surface plasmon polariton interaction channel. These phenomena pave the way for developing new flexible optical manipulators, allowing for control over a nanoparticle trajectory on subwavelength scales and opening opportunities for optical-induced anisotropic (i.e., with different periods along the field polarization as well as perpendicular to it) organization of particles on a plasmonic substrate., The authors acknowledge the support of the Russian Foundation for Basic Research (Grants No. 16-32-60167, No. 18-02-00414, No. 18-29-20063, and No. 18-52-00005). M.I.P. also acknowledges the support from the BASIS Foundation. A.S. acknowledges the support of the Ministry of Education and Science of the Russian Federation (GOSZADANIE, Grant No. 3.4982.2017/6.7). The force calculations were partially supported by Russian Science Foundation (Grant No. 18-72-10127). M.N.-V. is supported by the Spanish MINECO Grants No. FIS2012-36113-C03-03, No. FIS2014-55563-REDC, and No. FIS2015-69295-C3-1-P.

Being the polymorphs of calcium carbonate (CaCO3), vaterite and calcite have attracted a great deal of attention as promising biomaterials for drug delivery and tissue engineering applications. Furthermore, they are important biogenic minerals, enabling living organisms to reach specific functions. In nature, vaterite and calcite monocrystals typically form self-assembled polycrystal micro- and nanoparticles, also referred to as spherulites. Here, we demonstrate that alpine plants belonging to the Saxifraga genus can tailor light scattering channels and utilize multipole interference effect to improve light collection efficiency via producing CaCO3 polycrystal nanoparticles on the margins of their leaves. To provide a clear physical background behind this concept, we study optical properties of artificially synthesized vaterite nanospherulites and reveal the phenomenon of directional light scattering. Darkfield spectroscopy measurements are supported by a comprehensive numerical analysis, accounting for the complex microstructure of particles. We demonstrate the appearance of generalized Kerker condition, where several higher order multipoles interfere constructively in the forward direction, governing the interaction phenomenon. As a result, highly directive forward light scattering from vaterite nanospherulites is observed in the entire visible range. Furthermore, ex vivo studies of microstructure and optical properties of leaves for the alpine plants Saxifraga 'Southside Seedling' and Saxifraga Paniculata Ria are performed and underlined the importance of Kerker effect for these living organisms. Our results pave the way for a bioinspired strategy of efficient light collection by selfassembled polycrystal CaCO3 nanoparticles via tailoring light propagation directly to the photosynthetic tissue with minimal losses to undesired scattering channels., Comment: 20 pages, 6 figures

The ever‐growing field of microfluidics requires precise and flexible control over fluid flows at reduced scales. Current constraints demand a variety of controllable components to carry out several operations inside microchambers and microreactors. In this context, brand‐new nanophotonic approaches can significantly enhance existing capabilities providing unique functionalities via finely tuned light−matter interactions. A concept is proposed, featuring dual on‐chip functionality: boosted optically driven diffusion and nanoparticle sorting. High‐index dielectric nanoantennae is specially designed to ensure strongly enhanced spin−orbit angular momentum transfer from a laser beam to the scattered field. Hence, subwavelength optical nanovortices emerge driving spiral motion of plasmonic nanoparticles via the interplay between curl−spin optical forces and radiation pressure. The nanovortex size is an order of magnitude smaller than that provided by conventional beam‐based approaches. The nanoparticles mediate nanoconfined fluid motion enabling moving‐part‐free nanomixing inside a microchamber. Moreover, exploiting the nontrivial size dependence of the curled optical forces makes it possible to achieve precise nanoscale sorting of gold nanoparticles, demanded for on‐chip separation and filtering. Altogether, a versatile platform is introduced for further miniaturization of moving‐part‐free, optically driven microfluidic chips for fast chemical analysis, emulsion preparation, or chemical gradient generation with light‐controlled navigation of nanoparticles, viruses or biomolecules., The power of the spin−orbit coupling effect in all‐dielectric nanophotonics is harnessed to propose a novel, all‐optical nanomixing and sorting device potentially integrable in lab‐on‐a‐chip platforms. Specifically, under simple plane wave illumination, a dielectric structure with carefully tailored optical near fields is shown to induce nanofluid vortices, effectively boosting diffusion of admixtures.

We study optical binding of two dielectric nanoparticles near a boundary between air and hyperbolic metamaterial. Three kinds of modes contribution are analyzed and it is shown, that evanescent waves allow formation of stable bound dimer due to hyperbolic metamaterial modes. We have found the most profitable parameters of hyperbolic metamaterial substrate, providing enhancement of the optical binding effect.

The novel hybrid anapole states supported by dielectric nanoparticles are associated with the condition whem all the dominant Cartesian multipoles interfere destructively with their corresponding toroidal counterparts. They are characterized by a negligible light scattering for any observation direction. In the current work, we have proven the existence of high order hybrid anapole states in the visible range, resulting in a drastic reduction of the scattered radiation from a cylindrical nanoparticle with dimensions comparable to the wavelength. We demonstrate it by expanding the numerically calculated scattering cross section of the nanoparticle in terms of the Cartesian multipole decomposition. The simulations illustrate the simultaneous resonant suppression of the four leading multipole contributions to radiation (e.g. electric and magnetic dipoles and quadrupoles). Our results confirm the possibility to observe the effect experimentally, paving the way for future applications in dielectric nanophotonics.

Optical manipulation of small scatterers assisted with auxiliary nanostructures is a very promising and already proven concept. In this work, we investigate an interesting application of angular momentum transfer in light scattering by dielectric nanoparticles. We show that, when illuminated by a circularly polarized plane wave, the scattered Poynting vector from a homogeneous dielectric cube presents a divergence-free component. Such Poynting vector distribution induces rotational motion via angular momentum transfer to any strong absorbing particle in the vicinity of the scatterer. We illustrate this effect in the case perfectly absorbing dipolar nanoparticles. The proposed design is the first step towards an efficient all-dielectric mixing scheme for micro-fluidics applications.

Using metasurfaces, light can be manipulated beyond the limitations of classical optics. For instance, metasurfaces are used to widen the antenna aperture, to tailor light polarization, to be transparent, etc. Here, we study the effective fields in a magnetoelectric dipolar lattice positioned near PEC substrate. We show analytically that in the case of a subwavelength lattice spacing, the coupling between the electric and magnetic dipoles is induced mainly by the substrate reflected fields of dipoles at the coordinate of the perspective centre.

Vaterite is a very promising material for biological applications, but its electromagnetic properties have not been studied well enough. In this work we for the first time introduce multipole decompositions of subwavelength nanoparticles for dark field microscopy in optical range.

Here we use multipole decomposition approach to study optical properties of a silicon nanocylinder in different lossless media. We show that resonant peaks of multipole moments experience red shift, smoothing and broadening. Worth noting that electric multipoles experience bigger red shift than their magnetic counterparts. Our results can be applied to design optical devices within a single framework.

Dielectric nanophotonics is the modern and very relevant field of optics. In this work we use the recently reported Cartesian multipole decomposition approach for all-dielectric metasurfaces [1] to study optical properties of the silicon metasurface at the nanoscale. This metasurface consists of crystalline silicon cubes rotated by 45° around the axis perpendicular to the surface plane. We use numerical modeling and semi-analytical approach to find origins of the scatering by the considered metasurface. Results obtained with the multipole approach are in the good agreement with the direct calculations of transmission and reflection spectra. Insights from our study can be widely used to design novel metasurfaces and metadevices and tune their optical properties to achieve a needed functionality.

We report flexible optomechanical manipulations by the help of surface and volumetric modes of the substrate. Optical binding effect can be sufficiently enhanced due to both surface plasmon-polariton and hyperbolic modes of the structure. Volumetric modes of the structure provide optical pulling force for inclined incident plane wave, while surface waves cause enhancement of the optical trapping force under Gaussian beam illumination. Moreover, antitrapping effect can occur for specific positions of the beam waist.

The optical force acting on a nanoparticle near a planar substrate is governed by incident light and excitation of surface and volume modes of the substrate. We study system configurations leading to significant enhancement of optical forces, for example, plane wave results in pulling forces towards the source for certain types of anisotropic substrates.

Many modern optical instruments require the use of high-quality antireflecting coatings. Singleand multilayer homogeneous films are mainly used for this purpose. However, an alternative line is rapidly developed at present, which is devoted to the design and use of nanostructural systems for increasing the transparency of different media. Despite the unified principle of operation of these coatings, which is based on the destructive interference of waves in the direction of reflection of light, approaches to their implementation may differ significantly. Different types of nanostructural coatings are considered in detail and classified, their optical properties are compared, and special attention is paid to methods of their manufacture. It is shown that different antireflecting coatings should be used for different purposes, and that coatings that combine properties of several classes often have better antireflecting capabilities.

Optical activity is a fundamental phenomenon originating from the chiral nature of crystals and molecules. While intrinsic chiroptical responses of ordinary chiral materials to circularly polarized light are relatively weak, they can be enhanced by specially tailored nanostructures. Here, nanorod metamaterials, comprising a dense array of vertically aligned gold nanorods, is shown to provide significant enhancement of the circular dichroism response of an embedded material. A nanorod composite, acting as an artificial uniaxial crystal, is filled with chiral mercury sulfide nanocrystals embedded in a transparent polymer. The nanorod based metamaterial, being inherently achiral, enables optical activity enhancement or suppression. Unique properties of inherently achiral structures to tailor optical activities pave a way for flexible characterization of optical activity of molecules and nanocrystal-based compounds.

For the first time, we estimated perspectives for using a new 2D carbon nanotube (CNT)–graphene hybrid nanocomposite as a base element of a new generation o optical nanodevices. The 2D CNT–graphene hybrid nanocomposite was modelled by two graphene monolayers between which single-walled CNTs with different diameters were regularly arranged at different distances from each other. Spectra of the real and imaginary parts of the diagonal elements of the surface conductivity tensor for four topological models of the hybrid nanocomposite have been obtained. The absorption coefficient for p-polarized and s-polarized radiation was calculated for different topological models of the hybrid nanocomposite. It was found that the characteristic peaks with high intensity appear in the UV region at wavelengths from 150 to 350 nm (related to graphene) and in the optical range from 380 to 740 nm irrespective of the diameter of the tubes and the distance between them. For waves corresponding to the most intense peaks, the absorption coefficient as a function of the angle of incidence was calculated. It was shown that the optical properties of the hybrid nanocomposite were approximately equal for both metallic and semiconductor nanotubes.

Different optical nanostructures containing both loss and gain components attract ever-increasing attention as novel advanced materials and building blocks for a variety of nanophotonic and plasmonic applications. Unique tunable optical signatures of the so-called active metamaterials support their utilizing for sensing, imaging, and signal processing on micro- and nanoscales. However, this tunability requires flexible control over the metamaterials parameters, which could be provided by involving a set of nonlinear interactions. In this paper, we propose a method of governing ultrashort pulses by varying the level of a population difference disorder in a random active metamaterial. This enables to deliver three different interaction regimes: self-induced transparency (low disorder), localization regime (moderate disorder), and light amplification (strong disorder) corresponding to strongly different light pulses speeds. Since this control could be realized via rather plain tools, like simple pump tuning, the proposed disordered medium opens a room of opportunities for designing peculiar active component for a whole set of highly demanded optical applications., Comment: 8 pages, 6 figures + Supporting Information (5 pages, 6 figures)

Optical tweezers performance is investigated when the Gaussian beam is focused on the metal substrate with nanoparticle. When the beam is focused above the substrate optical force increases about an order of magnitude due to evanescent field of surface plasmon. Novel effect of repulsion from Gaussian beam (“anti-trapping”) is obtained when the beam waist is moved below the substrate which is confirmed by both the analytical approach and finite element simulation.

Spectral multipole resonances of parallelepiped-, pyramid-, and cone-like shaped silicon nanoparticles excited by linearly polarized light waves are theoretically investigated. The numerical finite element method is applied for the calculations of the scattering cross sections as a function of the nanoparticles geometrical parameters. The roles of multipole moments (up to the third order) in the scattering process are analyzed using the semianalytical multipole decomposition approach. The possibility of scattering pattern configuration due to the tuning of the multipole contributions to the total scattered waves is discussed and demonstrated. It is shown that cubic nanoparticles can provide a strong isotropic side scattering with minimization of the scattering in forward and backward directions. In the case of the pyramidal and conical nanoparticles the total suppression of the side scattering can be obtained. It was found that due to the shape factor of the pyramidal and conical nanoparticles their electric toroidal dipole resonance can be excited in the spectral region of the first electric and magnetic dipole resonances. The influence of the incident light directions on the optical response of the pyramidal and conical nanoparticles is discussed. The obtained results provide important information that can be used for the development of nanoantennas with improved functionality due to the directional scattering effects.

The work is devoted to the numerical simulation of circular dichroism amplification system based on a gold nano cuboids periodic array. We found the optimal configuration for amplifying circular dichroism by more than 30 times. We also demonstrated possible variants of optimization for achievement of controllable red shift of amplification band and amplification factor within variations of structure height, period and angle of incidence.

In this work we investigate lateral optical binding of two dielectric nanoparticles placed above a metallic substrate. We consider both longitudinal and lateral components of the optical binding force. Dyadic Green's function was used to describe analytically field distribution in the near and far field zone. Equilibrium positions for dielectric particles were calculated and contribution of metallic substrate was analyzed.

We explore the optical multipole resonances in silicon nanoparticles of a conical shape. We use the Finite Element Method (FEM) for solving the Maxwell equations for analysis of optical properties. Harnessing the multipole decomposition technique, we study excited optical resonances in silicon nanoparticles and the influence of high-order multipoles to scattering patterns of considered nanoparticles. Non-symmetrical combination of multipole contributions due to illumination from top and bottom sides of cones is also considered. Our work provides important information about the role of high order multipoles in the light scattering by non-spherical nanoparticles in the non-symmetrical case. Our results could be applied, for example, for development of metasurfaces and metamaterials in optical range, including asymmetrical ones.

Optical tweezers performance is investigated when the Gaussian beam is focused on the metal substrate with the subwavelength particle. Green's function is used to build analytical formalism underlining surface plasmon contribution to the optical force. Excitation of surface plasmon affects optical forces with significant impact at the surface plasmon resonance condition. At the next step the field and force are reconfigured by defocusing beam relative to the substrate. When the beam is focused above the substrate optical force increases about an order of magnitude due to evanescent field of surface plasmon. Novel effect of repulsion from Gaussian beam (“anti-trapping”) is obtained when the beam waist is moved below the substrate which is confirmed by both the analytical approach and finite element simulation. Anti-trapping of subwavelength dielectric particle can be applied for sorting of different-sized particles identical by shape and composition.

In this work we describe an ultraviolet subwavelength focusing in plasmonic nanostructures. A system which provides a 20–25 times local field enhancement at a wavelength of 350 nm is proposed. This system represents a metalized V-shaped groove in a surface of a dielectric medium. Subwavelength focusing is achieved by a plasmon wave propagation along the surface of metal film and by the transfer of electromagnetic field through the dielectric medium. The influence of system parameters on a local field enhancement is investigated. A simplified model that allows for determining the geometric parameters of an optimized resonator is proposed.

For a long time, light manipulation at the nanoscale has been provided primarily with plasmonic materials. However, recent works show that the light can be controlled with dielectric particles. Here, we exploit the asymmetric shape of silicon nanopyramids to control the far-field scattering pattern and the electric field concentration inside the particles by simply changing the incident light polarization. This effect is considered both in air and lossless optical medium. For an explanation of the demonstrated features, we apply the multipole analysis of the scattering cross sections. We show that the electric and magnetic quadrupole resonances can be switched between them by changing the incident wave polarization providing changes of the scattering diagrams. We also show that the polarization control of the scattering properties of pyramidal nanoparticles strongly depends on the refractive index of the surrounding medium. The obtained results can be used for the development of optical antennas, switchers, and polarization filters composed of silicon materials.

In order to achieve interaction between light beams, a mediating material object is required. Nonlinear materials are commonly used for this purpose. Here a new approach to control light with light, based on a nano-opto-mechanical system integrated in a plasmonic waveguide is proposed. Optomechanics of a free-floating resonant nanoparticle in a subwavelength plasmonic V-groove waveguide is studied. It is shown that nanoparticle auto-oscillations in the waveguide induced by a control light result in the periodic modulation of a transmitted plasmonic signal. The modulation depth of 10% per single nanoparticle of 25 nm diameter with the clock frequencies of tens of MHz and the record low energy-per-bit energies of 10−18 J is observed. The frequency of auto-oscillations depends on the intensity of the continuous control light. The efficient modulation and deep-subwavelength dimensions make this nano-optomechanical system of significant interest for opto-electronic and opto-fluidic technologies.

Possibility of magnetic energy accumulation inside silicon nanoparticles at the conditions of resonant optical responses is investigated theoretically. The magnetic field distributions inside silicon nanocylinders with and without coaxial through holes are calculated using full-wave numerical approach. It is demonstrated that such systems can be used for control and manipulation of optical magnetic fields providing their enhancement up to 26 times at the condition of optical resonances. Obtained results can be used for realization of nanoantennas and nanolasers, in which magnetic optical transitions play significant roles., 12 pages, 4 figures

In this work, we investigate the efiect of broadband antire∞ection of a medium by a layer of embedded nano-cavities arranged near the surface. It is shown that this structure is versatile and allows near 100% transmittance in a wide spectral range practically for any dielectric material. The approximate model of nano-structured layer is suggested that allows to determine the parameters of the system necessary for achieving antire∞ection of any a priori given media without complicated numerical calculations. The transmission spectrum of a medium modifled by such a structure is entirely deflned by a radius and a depth of bedding of the nano-porous layer.

All-dielectric “magnetic light” nanophotonics based on high refractive index nanoparticles allows controlling magnetic component of light at nanoscale without having high dissipative losses. The artificial magnetic optical response of such nanoparticles originates from circular displacement currents excited inside those structures and strongly depends on geometry and dispersion of optical materials. Here an approach for enhancing of magnetic response via resonant bianisotropy effect is proposed and analyzed. The key mechanism of enhancement is based on electric-magnetic interaction between two electrically and magnetically resonant nanoparticles of all-dielectric dimer. It was shown that proper geometrical arrangement of the dimer in respect to the incident illumination direction allows flexible control over all vectorial components of the magnetic moment, tailoring the latter in the dynamical range of 100% and delivering enhancement up to 36% relative to performances of standalone spherical particles. The proposed approach provides pathways for designs of all-dielectric metamaterials and metasurfaces with strong magnetic responses.

We suggest a model of an optical structure that allows to accelerate nanoparticles to velocities on the order of tens of centimeters per second using low-intensity external optical fields. The nano-accelerator system employs metallic V-grooves which concentrate the electric field in the vicinity of their bottoms and creates large optical gradient forces for the nanoparticles in that groove. The conditions are found when this optical force tends to eject particles away from the groove.

Optical properties of spatially ordered nanocomposites consisting of spherical dielectric and metallic nanoparticles have been investigated. On the basis of the method of integral equations, expressions for the field inside and outside the system have been derived and studied. It has been shown that, depending on the material and geometrical parameters of the nanoaggregate, two different states of the system can be obtained, which differ in the presence or absence of a band gap (interference reflection peak) in the visible range for photons with a certain energy. It is shown that at definite parameters of the nanostructure the scattering and absorption of light by nanoparticles diminishes and the ensemble under consideration becomes transparent. The position of the spectral ranges of transparency of metallic composites on the wavelength scale in this case is determined by the frequency of the polariton resonance inherent in the nanoclusters that form the nanocomposite. A heterogeneous material formed of close-packed dielectric nanospheres is suggested, which at some wavelengths possesses a 100% light transmission.