Vladimir P. Dzyuba

van der Waals metal-organic framework as an excitonic material for advanced photonics

Synergistic combination of organic and inorganic nature in van der Waals metal-organic frameworks supports different types of robust excitons that can be effectively and independently manipulated by light at room temperature, and opens new concepts for all-optical data processing and storage.

Photo-induced electric polarizability of Fe3O4 nanoparticles in weak optical fields

Using a developed co-precipitation method, we synthesized spherical Fe3O4 nanoparticles with a wide nonlinear absorption band of visible radiation. Optical properties of the synthesized nanoparticles dispersed in an optically transparent copolymer of methyl methacrylate with styrene were studied by optical spectroscopy and z-scan techniques. We found that the electric polarizability of Fe3O4 nanoparticles is altered by low-intensity visible radiation (I ≤ 0.2 kW/cm2; λ = 442 and 561 nm) and reaches a value of 107 Å3. The change in polarizability is induced by the intraband phototransition of charge carriers. This optical effect may be employed to improve the drug uptake properties of Fe3O4 nanoparticles.PACS33.15.Kr, 78.67.Bf, 42.70.Nq

Binding energy of excitons formed from spatially separated electrons and holes in insulating quantum dots

It is found that the binding energy of the ground state of an exciton formed from an electron and a hole spatially separated from each other (the hole is moving within a quantum dot, and the electron is localized above the spherical (quantum dot)–(insulating matrix) interface) in a nanosystem containing insulating Al2O3 quantum dots is substantially increased (by nearly two orders of magnitude) compared to the exciton binding energy in an Al2O3 single crystal. It is established that, in the band gap of an Al2O3 nanoparticle, a band of exciton states (formed from spatially separated electrons and holes) appears. It is shown that there exists the possibility of experimentally detecting the ground and excited exciton states in the band gap of Al2O3 nanoparticles at room temperature from the absorption spectrum of the nanosystem.

Nontypical photoinduced optical nonlinearity of dielectric nanostructures

The recently discovered ultralow-threshold nonlinear refraction of low-intensity laser radiation in dielectric nanostructures has an atypical dependence on radiation intensity in the pulsedandcontinuousmodes.Wefirstcarryoutquantitativemeasurementsofthedependenceof the nonlinear response of liquid dielectric nanostructures on the low-intensity radiation and then devise a theoretical explanation. The theory suggests that the nonlinearity is of photoinduced nature instead of a thermal one and depends directly on the nanoparticles electronic structure and the relationship between permittivities of dielectric matrix and nanoparticles. C � 2011 Society

Quantum-Size States of a Particle inside the Deformed Nanosphere

In this paper we propose an original functional method which allows us to determine the effect of different deviations of nano-object shape on quantum characteristics of particles localized inside the nano-object. This method is ideologically similar to the perturbation theory, but the perturbation of the surface shape, rather than potential, is used. The results of analysis the quantum-size states of particles inside the nano-object with deformed sphere shape showed that the probability density of particle location is more sensitive to shape perturbations than surface energy spectrum and quantum states density are.

Quantum-size states of the deformed nanosphere

The effect of shape deformation of a spherical nano-object on quantum states of a particle in it has been analyzed theoretically. For this purpose, a functional method of surface shape perturbation theory has been proposed. The method allows us to determine the effect of a wide range of deviations of a limited three-dimensional volume (nano-object) from the initial shape on the quantum characteristics of a charge localized inside the nano-object. An analysis has demonstrated that the probability density for a particle in quantum-size states is more sensitive to surface shape perturbations than the energy spectrum and the density of quantum states. Even small shape perturbations lead to a smearing of the probability density for the location of a particle inside a nano-object and lift the degeneracy in the magnetic quantum number. A mixing of pure states corresponding to a sphere has been observed. The degree of mixing and the splitting of the energy levels increase with increasing quantum numbers l and m.

Biexciton in nanoheterostructures of dielectric quantum dots

Abstract. It has been found that the formation of a biexciton in a nanoheterostructures (NHS) made up of aluminum oxide quantum dots (QDs) synthesized in a dielectric matrix is of threshold character and can occur in a nanosystem, where the distance D between the surfaces of QD is given by the condition Dc(1)≤D≤Dc(2). We have shown that with such an NHS acting as “exciton molecules” (biexcitons consisting of spatially separated electrons and holes) are the QDs of aluminum oxide with excitons localizing over their surfaces. The position of the biexciton state energy band depends both on the mean radius of the QDs, and the distance between their surfaces, which enables one to purposefully control it by varying these parameters of the nanostructure.

Dielectric Nano-Systems with Unique Optical Properties

The study of optical properties of Al2O3, SiO2, TiO2, and ZnO nanoparticles in weak optical fields is presented. We found that some nanoparticles have unique optical nonlinearity: The values of portions to nanoparticle refractive index and absorption coefficient increase to maxima, and then decrease to zero when the radiation intensity changes from 1 to 500 W/cm2. We estimated electron energy structures of nanoparticles and experimentally determined that such nonlinearity is directly related to peculiarities of the energy structure. We obtained a good fitting of theoretical results to the experimental ones (e.g. absorbance spectra of nanoparticles; the dependence of nanoparticle refractive index and absorption coefficient on radiation intensity).

Phase function method in problems of acoustic wave scattering

A generalization of the phase function method known in quantum mechanics to the problems of acoustic wave scattering on continuous medium inhomogeneities is proposed. The idea of the use of this method in acoustics is based on the fact that the wave equation for the acoustic potential or pressure in an inhomogeneous medium is reduced to the Schrödinger equation with a variable scattered field potential by a special substitution.

Photonics of Heterogeneous Dielectric Nanostructures

Over last 20 years great scientific attention has been paid to nanostructures and nanocompo‐ sites based on nanoparticles of semiconductor materials (1eV<Egap<3eV) since they exhibit a wide range of nonlinear properties and can be used in various applied fields [1-5]. However, the history of active investigation of dielectric nanostructures’ properties started only recently [6-8]. These structures are the heterogeneous medium formed by liquid or solid dielectric ma‐ trices (e.g., polymer glasses and oils) and nanoparticles of dielectrics (Al2O3, SiO2, MgO, etc.).