Constraints on transmission, dispersion, and density of states in dielectric multilayers and stepwise potential barriers with arbitrary layer arrangement

Normal-incidence transmission and dispersion properties of optical multilayers and one-dimensional stepwise potential barriers in the non-tunneling regime are analytically investigated. The optical paths of every constituent layer in a multilayer structure, as well as the parameters of every step of the stepwise potential barrier, are constrained by a generalized quarter-wave condition. No other restrictions on the structure geometry is imposed, i.e., the layers are arranged arbitrarily. We show that the density of states (DOS) spectra of the multilayer or barrier in question are subject to integral conservation rules similar to the Barnett-Loudon sum rule but ocurring within a finite frequency or energy interval. In the optical case, these frequency intervals are regular. For the potential barriers, only non-periodic energy intervals can be present in the spectrum of any given structure, and only if the parameters of constituent potential steps are properly chosen. Abstract The integral conservation relations derived analytically have also been verified numerically. The relations can be used in dispersion-engineered multilayer-based devices, e.g., ultrashort pulse compressors or ultracompact optical delay lines, as well as to design multiple-quantum-well electronic heterostructures with engineered DOS.Comment: 10 pages, 5 figures, to be submitted to PR

Problems of Threats to Russia’s Economic Security in Cooperation with the Countries of the Eurasian Economic Union in the Context of Administrative and Legal Regulation

The paper examines topical the problems of minimizing threats to Russia’s economic security when interacting with the countries of the Eurasian Economic Union in the context of administrative and legal regulation, problems arising in the organization of this work and the direction of their improvement. The objective of the study is to comprehensively study, analyze and summarize the theoretical provisions and results of practical activities in the sphere of minimizing threats to Russia’s economic security when interacting with the countries of the Eurasian Economic Union in the context of administrative and legal regulation. Methodology: Approved scientific methods for the comprehensive study of phenomena and processes in their interdependence and, above all, the didactic method of cognition. In the process of collection and processing of empirical material, the author used a comprehensive, systemic, axiological and synergetic approaches that ensure a comprehensive study of the problems of minimizing threats to Russia’s economic security when interacting with the countries of the Eurasian Economic Union in the context of administrative and legal regulation. Results: it is necessary to confess that government activity on providing of economic security and defense of national interests of country in area of economy must come true on permanent basis.     Keywords: minimization of threats of economic security to Russia; Eurasian Economic Union; administrative legal regulation; system of theoretical knowledge and practical recommendations of minimization of threats of economic security to Russia at cooperating with the countries of the Eurasian economic union; assistance to development of small and middle enterprise due to the decline of financial and administrative expenses; diagnostics and monitoring of economic strength security

Josephson surface plasmons in spatially confined cuprate superconductors

In this work, we generalize the theory of localized surface plasmons to the case of high-Tc cuprate superconductors, spatially confined in the form of small spherical particles. At variance from ordinary metals, cuprate superconductors are characterized by a low-energy bulk excitation known as the Josephson plasma wave (JPW), arising from interlayer tunneling of the condensate along the c-axis. The effect of the JPW is revealed in a characteristic spectrum of surface excitations, which we call Josephson surface plasmons. Our results, which apply to any material with a strongly anisotropic electromagnetic response, are worked out in detail for the case of multilayered superconductors supporting both low-frequency (acoustic) and transverse-optical JPW. Spatial confinement of the Josephson plasma waves may represent a new degree of freedom to engineer their frequencies and to explore the link between interlayer tunnelling and high-Tc superconductivity

Exciton spin dynamics in spherical CdS quantum dots

Exciton spin dynamics in quasi-spherical CdS quantum dots is studied in detail experimentally and theoretically. Exciton states are calculated using the 6-band k.p Hamiltonian. It is shown that for various sets of Luttinger parameters, when the wurtzite lattice crystal field splitting and Coulomb interaction between the electron-hole pair are taken into account exactly, both the electron and hole wavefunction in the lowest exciton state are of S-type. This rules out the spatial-symmetry-induced origin of the dark exciton in CdS quantum dots. The exciton bleaching dynamics is studied using time- and polarization-resolved transient absorption technique of ultrafast laser spectroscopy. Several samples with a different mean size of CdS quantum dots in different glass matrices were investigated. This enabled the separation of effects that are typical for one particular sample from those that are general for this type of material. The experimentally determined dependence of the electron spin relaxation rate on the radius of quantum dots agrees well with that computed theoretically.Comment: 24 pages, 10 figure

Channel spaser

We show that net amplification of surface plasmons is achieved in channel in a metal plate due to nonradiative excitation by quantum dots. This makes possible lossless plasmon transmission lines in the channel as well as the amplification and generation of coherent surface plasmons. As an example, a ring channel spaser is considered

Investigation of anatomical signs of canadian goldenrod herbs, introduced in Ukraine

The monograph «Goldenrod» SPhU 2.0 describes the general morphological and anatomical features of two species – Solidago gigantea Ait and Solidago canadensis L., which are similar. Not all diagnostic signs can be identified in powdered raw materials. It was important to investigate domestic series of сanadian goldenrod and to identify additional diagnostic signs. The aim of the work was to study the series of domestic raw materials of сanadian goldenrod by anatomical features and to determine the totality of individual features of the species to establish the identity of raw materials. The object of the study were samples of сanadian goldenrod grass, which were harvested in August 2020 in the regions of Ukraine. We used an iPhone XR camera, Item PB-2610 V microscope. Important features of the anatomical structure of the raw material of сanadian goldenrod include: the cells of the stem epidermis are parenchymal, ortho-walled, porous, the leaves – sinuous- and ortho-walled. The presence in the pubescence of stems and leaves 3 types of hairs: simple long, 5–8-celled (up to 20), with thickened walls and pointed cell; short, 2–3-celled, with a dormant apical cell; short and headed with a 2–3-celled stalk and a rounded unicellular head; on the surface and edge of the leaves of the involucre – simple short and 3–4-cell hairs, corollas of flowers – multicellular double-row hairs; stem vessels are spiral, ladder, porous and reticulate; schizogenous structures in the stems, leaves and leaves of the involucre; sphenocrystals of inulin in the parenchyma and vessels of the stem, the cells of the corollas of flowers. A series of domestic raw materials of сanadian goldenrod has been studied according to anatomical features, a set of individual features of the species has been determined. The obtained results can be used in plant taxonomy for comparative analysis of morphologically similar species of the genus Zolotushnik, as well as to supplement the section «Identification B» of the monograph SPhU 2.0 «Zolotushnik»