Institute of High Technology

We consider a one-dimensional scattering problem and establish a system of two integral equations for the local ͑self-consistent͒ electric field. The equations are derived using the standard Green's function method. Their solution yields the local fields at any point of the system. To illustrate the efficacy of this approach, we apply it to a film and obtain analytical solutions that are identical to the Fabry-Perot solution. Some potential applications of the approach are also discussed.

The effective susceptibility concept is developed for solution of electrodynamical problems of nano-systems. General principles of introducing effective susceptibility are discussed. The effective susceptibility for different nano-systems, namely, thin films, mesoparticles and quantum dots were calculated. Some examples of effective susceptibility uses were demonstrated. In part, the absorption profiles when inhomogeneous along the thickness thin film absorbs the light, was calculated. Discussed concept was used to show the influence of the shape of nano-partiles covering the surface on dispersion of surface plasmon polaritons. It was shown that proposed approach can be useful for analysis of surface plasmon polarriton resonance experiments. The effective susceptibility concept is useful for modeling of near-field images of linear and nonlinear scanning near-field optical microscopy. The presented method can be applied for modeling of near-field images of different objects. For example, there are pyramid-like quantum dots and semiconductor surface excited by strong focused Gauss-like beam of the light.

The effective susceptibility concept is developed for solution of electrodynamical problems of nano-systems. General principles of introducing effective susceptibility are discussed. The effective susceptibility for different nano-systems, namely, thin films, mesoparticles and quantum dots were calculated. Some examples of effective susceptibility uses were demonstrated. In part, the absorption profiles when inhomogeneous along the thickness thin film absorbs the light, was calculated. Discussed concept was used to show the influence of the shape of nano-partiles covering the surface on dispersion of surface plasmon polaritons. It was shown that proposed approach can be useful for analysis of surface plasmon polarriton resonance experiments. The effective susceptibility concept is useful for modeling of near-field images of linear and nonlinear scanning near-field optical microscopy. The presented method can be applied for modeling of near-field images of different objects. For example, there are pyramid-like quantum dots and semiconductor surface excited by strong focused Gauss-like beam of the light.

A self-consistent analytical approach was developed to describe the optical properties of an assembly of magneto-plasmonic composite nanoparticles distributed on a dielectric substrate. The proposed theory is based on the effective susceptibility concept in the frame of Green's function method and accounts for the local-field effects in the system. The analytical expressions for effective susceptibility of a single particle, as well as for assemblies of particles, on the substrate were derived to treat the scattered electromagnetic field by an assembly of composite nanoparticles. The developed formalism was applied to describe the polar Kerr effect in the Au/Co-based magneto-plasmonic system. The results of the simulation suggest that the magneto-optical properties of the considered magneto-plasmonic composite are determined by the interplay between "particleparticle" and "particle-surface" interactions, which are mainly given by the geometry of the particles, their concentration, and the optical properties of the substrate.

The theoretical aspects of visualization of nano-objects by scattering of surface plasmon-polariton are discussed in the frame of local-field approach. It was shown that the image intensity obtained with the optical objective depends on the dimension of nano-object. In part, it was obtained that the dependence of intensity on the nano-particle dimension is a linear, when the distance between the falling edge of the particle and a surface is much lesser than particle dimension, and is proportional to particle volume, when the distance is about of particle dimension. The results of calculations were compared with experimental data obtained by different scientific teams.

Reflection of light by a polar ferromagnetic insulator in the reststrahlen band region is theoretically studied. Under certain conditions a narrow frequency band inside this region can be found which permits light to transmit through the crystal.

The interaction between two spheres with the use of a macroscopic selfconsistent approach allowing one to rigorously describe multiple scattering in near-field optics is considered. The implementation of this approach leads to the concept of the effective susceptibility of the scattering system that explicitly relates the incident field to the self-consistent field. We demonstrate that the approach developed can be advantageously used to determine the self-consistent field in systems with simple geometry. Considering two interacting spherical scatterers we show that the self-consistent fields inside the spheres, calculated with and without taking into account multiple scattering, differ noticeably at a resonance.

We present a self-consistent approach based on Green's function formalism allowing us to calculate local electromagnetic properties of a complex system consisting of a single-electron spherical quantum dot (QD) interacting with a dielectric mesoparticle. The cases of static and frequency dependent dielectric permittivity of the mesoparticle were considered. In the static case, due to the coupling between the QD and the mesoparticle, the absorption spectrum of the QD gets redshifted. In the frequency dependent case, the absorption line splits into two peaks. The strongest splitting was observed when the resonance frequency of the mesoparticle is close to the transition frequency of the QD. The interaction effects depend on the polarization of the incident light and diminish with increasing of the interparticle distance.

An exact analytical solution of the self-consistent equation for the local ÿeld is used to calculate the near-ÿeld optical images of pyramid-like nano-objects placed at a surface of a solid. The diagram method developed previously for near-ÿeld image formation is generalized in order to describe layered objects, which are treated as many-body systems. The near-ÿeld optical images of triangular and square pyramids are calculated for the illumination conÿguration as well as those of triangular and square prisms. It is found that the near-ÿeld images of nanoparticles having the dielectric constant close to that of the substrate change rapidly and in a complicated manner with the probe-sample distance.

The self-consistent approach is proposed for calculation of an e ective susceptibility of single nano-particle and nano-particle layer at a surface of a solid. This approach is based on exact summation of iteration procedure series, which is applied to solution of self-consistent equation for a local ÿeld. The condition when the layer can be considered as dilute one is discussed.

The concentration of surface molecules N s and components of molecular susceptibility jl (ω) can both be determined from surface plasmon-polariton resonance (SPPR) experiments, instead of effective layer thickness and index of refraction, which are usually determined. The theoretical consideration of a molecular layer as monolayer of separated 3D-oscillators provides a new perspective for investigating molecules during SPPR experiment. It is shown that SPPR response and the form of the reflective curve depend on the form of a biomolecule and its orientation relative to the surface of the metal-carrier of plasmon oscillations. The experimental data for immunological reaction for the calculation of surface molecular concentration and mass of biomolecular covering are presented.

Nanocomposite films consisting of gold inclusions in the polytetrafluoroethylene (PTFE) matrix were obtained by thermal vacuum deposition. Annealing of the obtained films with different temperatures was used to measure varying of film morphologies. The dependence of optical properties of the films on their morphology was studied. It was established that absorption and profile of the nanocomposite film obtained by thermal vacuum deposition can be changed with annealing owing to the fact that different annealing temperatures lead to different average particle sizes. A method to calculate the optical properties of nanocomposite thin films with inclusions of different sizes was proposed. Thus, comparison of experimental optical spectra with the spectra obtained during the simulation enables estimating average sizes of inclusions. The calculations give the possibility of understanding morphological changes in the structures.

This article presents results of theoretical description and numerical modeling of processes like Raman scattering by molecular layers obtained with account of lateral interactions in such layers. Green functions for a half-space with an ultra-thin film is obtained from a self-consistent Dyson equation. Expression for the response of such a system on shifted frequency, which has straightforward physical interpretation, is given. It is shown that lateral interactions create new modes localized on the ultra-thin film and it is the interaction with these modes, which can enhance response of such a film in different processes. Numerical calculations based on the presented theoretical results exhibit the possibility to enhance Raman scattering by adsorbed molecules both for p-and s-polarized light. Detailed qualitative analysis of these processes clearly demonstrates that enhancement may be reached just by interaction with discussed modes. Obtained enhancement is not giant for Raman scattering, but it is remarkable and can be reached for any light polarization and for bigger variety of systems than surface enhanced Raman scattering can.

Enhancement of the spontaneous decay rate due to local-field effects is estimated for a luminous dipole inside a small dielectric particle. To do this, we make use of an idea on multiplicativity of the local-field factor. Elongated particles are shown to be promising in respect of the local-field enhancement of the spontaneous emission. Computations are carried out within the framework of modern theory of the spontaneous decay of excited atoms in absorbing media for both the virtualcavity and real-cavity models. Particular emphasis is placed on dielectric/semiconductor particles in the vicinity of the optical phonon frequencies.

An implementation of plasmon resonances in nanocomposite thin films for biosensors is discussed. The effect is studied in the system of modified Au inclusions inside the Teflon matrix. The optical response of the nanocomposite thin film with inhomogeneous distribution of embedded coated Au spherical nanoparticles across the film thickness is analyzed. The absorption profiles are calculated in a case of light incidence normally to the film surface. Their dependences on volume fractions and spatial distributions of inclusion nanoparticles across the film thickness are discussed for some values of the film thickness. The obtained absorption profiles depending on the characteristics of the shell of nanoinclusions allow proposing the optical control method for the biospecific reactions at the surface of modified nanoinclusions.

The antiviral activity of nonfunctionalized gold nanoparticles (AuNPs) against herpes simplex virus type-1 (HSV-1) in vitro was revealed in this study. We found that AuNPs are capable of reducing the cytopathic effect (CPE) of HSV-1 in Vero cells in a dose- and time-dependent manner when used in pretreatment mode. The demonstrated antiviral activity was within the nontoxic concentration range of AuNPs. Interestingly, we noted that nanoparticles with smaller sizes reduced the CPE of HSV-1 more effectively than larger ones. The observed phenomenon can be tentatively explained by the near-field action of nanoparticles at the virus envelope. These results show that AuNPs can be considered as potential candidates for the treatment of HSV-1 infections.

The main purpose of the work is to clarify the physical mechanisms which leads to the specific spectrums of the structures [1-3]. The work is based on the ideas of the effective susceptibility. The effective susceptibility of cone-shaped nanohills located at the semiconductor surface is obtained in the frame of local-field approach. The knowledge of the effective susceptibility allows to calculate the optical absorption profiles. Using the approach similar to Levshin rule the photoluminescence spectra were calculated. Obtained results were compared with experimental luminescence spectra obtained earlier. The significant machanisms, that define the peculiarities of the spectra, is the shape of the nanoclasters and the inhomogeneity of the nanohills array are justificated. The main issue of the work is that the cause of the luminescence spectrums has electodynamical nature without spatial quantisation effects.

The macroscopic approach that allows one to obtain an exact solution of the self-consistent equation of the Lippmann-Schwinger type is developed. The main idea of our method consist in usage of diagram technique for exact summation of the infinite series corresponding to the iteration procedure for solving the self-consistent integral equation. The method developed is applied to calculations of near-field optical images obtained in illumination mode. It is assumed that the system under consideration consists of an object illuminated by the field scattered by a small probe. This assumption allows us to consider multiple scattering between a (point-like) probe and an extended object as well as inside the object. The exact solution for the self-consistent field is then obtained in terms of effective susceptibility of the probe-object system. Application of our method to the description of orientation of molecular complexes at the surface is discussed.