Propagation of nonclassical light in structured media

In the present thesis the propagation of nonclassical light in structured media is studied with the accounting of various loss mechanisms. First, the characterization of nonclassicality of quantum light being in contact with a thermal bath is given. For the description of nonclassical light propagation through the optical cavities the method of replacement schemes for modeling the loss mechanisms is proposed. Finally, the propagation of light in a semiconductor media with boundaries with account of absorption, dispersion, spatial inhomogeneity and spontaneous emission effects on the nonclassical properties of squeezed light are studied.Das Ziel der vorliegenden Promotionsthesen ist die theoretische Beschreibung von nichtklassischem Licht in strukturierten Medien. Zunächst wurde eine Charakterisierung von nichtklassischem Licht im Kontakt mit einem thermischen Bad durchgeführt. Mit dem Ziel der vollständigen Charakterisierung aller möglichen Verlustmechanismen in optischen Resonatoren wurde die Methode der "Replacement-Schemes" entwickelt. Es wird auch die Ausbreitung von Licht in begrenzten Halbleitermedien betrachtet. Die Einflüsse von Absorption, Dispersion, räumlichen Inhomogenitäten und spontaner Emission auf die nichtklassischen Eigenschaften von gequetschtem Licht wurden untersucht

СОВРЕМЕННЫЕ ПРЕДСТАВЛЕНИЯ О ХАРАКТЕРЕ ФОРМИРОВАНИЯ ТВЁРДОЙ КОРОЧКИ В КРИСТАЛИЗАТОРЕ

The nature of the formation of a hard crust in the mold is studied, taking into account the shrinkage of the workpiece during solidification. Comparison of the geometric shapes of the sleeves of the leading manufacturers from Germany, Italy, Japan. It is shown that defects in the billet crust originating in the mold cannot be corrected by subsequent cooling conditions. At the exit from the mold, the ingot crust must be of uniform thickness and withstand the ferrostatic pressure of liquid steel in order to prevent metal breakthroughs. This requires the organization of an intensive and continuous heat removal from the liquid steel to the cooling water in the crystallizer. The processes of heat removal from the surface of the solid crust of the workpiece through the walls of the mold liner are of decisive importance from the point of view of the dynamics of the growth of the solid phase and, as a consequence, the formation of surface and subsurface defects. To ensure high productivity and the required surface quality of the billet, leading companies strive to optimize the geometric shape of the mold sleeve, departing from classical designs.Изучен характер формирования твердой корочки в кристаллизаторе, учитывая усадку заготовки при затвердевании. Проведено сравнение геометрических форм гильз ведущих производителей из Германии, Италии, Японии. Показано, что дефекты, зарождающейся в кристаллизаторе корочки заготовки, невозможно исправить последующими условиями охлаждения. На выходе из кристаллизатора корочка слитка должна быть равномерной толщины и выдерживать ферростатическое давление жидкой стали, чтобы предотвратить прорывы металла. Для этого требуется организация интенсивного и непрерывного таплоотвода от жидкой стали к охлаждающей воде в кристаллизаторе. Процессы отвода тепла от поверхности твердой корочки заготовки через стенки гильзы кристаллизатора имеют определяющее значение с точки зрения динамики нарастания твердой фазы и, как следствие, формирования поверхностных и подповерхностных дефектов. Для обеспечения высокой производительности и требуемого качества поверхности заготовки, ведущие фирмы стремятся к оптимизации геометрической формы гильзы кристаллизатора, отходя от классических конструкций

Satellite-mediated quantum atmospheric links

The establishment of quantum communication links over a global scale is enabled by satellite nodes. We examine the influence of the Earth's atmosphere on the performance of quantum optical communication channels with emphasis on the downlink scenario. We derive the geometrical path length between a moving low Earth orbit satellite and an optical ground station as a function of the ground observer's zenith angle, his geographical latitude, and the meridian inclination angle of the satellite. We show that the signal distortions due to regular atmospheric refraction, atmospheric absorption, and turbulence have a strong dependence on the zenith angle. The observed saturation of transmittance fluctuations for large zenith angles is explained. The probability distribution of the transmittance for slant propagation paths is derived, which enables us to perform the security analysis of decoy-state protocols implemented via satellite-mediated links

Joint Impedance Spectroscopy and Fractography Data Analysis of Ceria Doped Scandia Stabilized Zirconia Solid Electrolyte modified by powder types and sintering temperature

Parameters of the non-Debye relaxation in the 10Sc1CeSZ solid electrolyte made of various types of ZrO2 powder stabilized with 10-mol.% Sc2O3 and 1-mol.% CeO2 were studied. The influence of powder properties and their sintering temperatures on the impedance spectra is analyzed. In regard to electrical response, the polycrystalline ceramic electrolytes may be considered as a single-phase or a two-phase material consisting of a grain bulk and a boundary. In many cases, the boundary resistance is independent practically on dopants and their distribution across the powders and sintering temperatures. The powder compositions suitable for an electrolyte and electrodes are specified

Anisotropic scintillation indices for low elevation angles

This contribution deals with the extension of the flat-earth model to a spherical one. The correlation properties of ionospheric electron density fluctuations responsible for scintillation occurrence are modeled conventionally as the ellipsoidal surfaces of constant value for the autocorrelation. The relative position of such ellipsoids and the radio-wave ray path modulates the scintillation strength and has purely geometrical origin. The information on communication link geometry is used for proper generation of phase screens used further for simulation of wave propagation through randomly inhomogeneous ionosphere. For clarity and simplicity we have used also the single phase screen model and derived the analytic formulas for amplitude and phase scintillation indices following the approach of C. Rino'79. We show that the accounting of the finiteness of earth-/ ionospheric-shell- curvature yields the non-divergent values for scintillation indices at low elevation angles. Additionally to this, the regions of geometric enhancement of scintillation at low elevations appear to be displaced from the corresponding regions predicted within the flat-earth approximation. The found discrepancy is important for proper determination of regions of high scintillation activity at high latitudes, e.g., as regions mapped on sky plots for a certain groundbased receiver. Incorporation of the proposed geometric model in the scintillation climatological models such as the GISM or the WBMOD will be consistent with their extension to low elevation angles and, hence, will be useful for some aforementioned user-cases. C. L. Rino, "A power law phase screen model for ionospheric scintillation: 1. Weak scatter," Radio Sci., 14, November 1979, pp. 1135-1145, doi: 10.1029/RS014i006p01135

Modeling of ionospheric scintillation

A signal, such as from a GNSS satellite or microwave sounding system, propagating in the randomly inhomogeneous ionosphere, experiences chaotic modulations of its amplitude and phase. This effect is known as scintillation. This article reviews basic theoretical concepts and simulation strategies for modeling the scintillation phenomenon. We focused our attention primarily on the methods connected with the random phase screen model. For a weak scattering regime on random ionospheric irregularities, a single phase screen model enables us to obtain the analytic expression for phase and intensity scintillation indices, as well as the statistical quantities characterizing the strength of scintillation-related fades and distortions. In the case of multiple scattering, the simulation with multiple phase screens becomes a handy tool for obtaining these indices. For both scattering regimes, the statistical properties of the ionospheric random medium play an important role in scintillation modeling and are discussed with an emphasis on related geometric aspects. As an illustration, the phase screen simulation approaches used in the global climatological scintillation model GISM is briefly discusse

Geometric enhancement for scintillation modeling

Continuous improvement of scintillation models is an important task required for adequate analysis and prediction of scintillation events caused by ionospheric irregularities. Some improvement can be achieved by an improved geometric description of small-scale perturbations in the ionosphere. Recently we revise the classical results of Ref. [1] obtained in the flat-earth approximation and generalized them for the case when the finite curvature of the earth has to be considered. Assuming that the earth is spherical, we obtained the analytic expressions for phase and intensity scintillation indices [2] in the approximation of a single thin phase changing screen. The obtained results for spherical-earth geometry are divergence-free and represent the appropriate position of the enhancement maximum as a function of the dip angle for field-aligned ionospheric irregularities. Thus, the spherical-earth model is suitable for scintillation modeling and forecasting in such user cases as limb sounding, reflectometry, positioning at small elevation angles. Implementation of the proposed geometric considerations in the Global Ionospheric Scintillation Model is also briefly discussed 1 C. L. Rino, "A power law phase screen model for ionospheric scintillation: 1. Weak scatter," Radio Sci., 14, 1135 (1979) 2 D.V. Vasylyev, Y. Bèniguel, M. Kriegel, V. Wilken, J. Berdermann, "Modeling ionospheric scintillation," 12, 22, (2022

Geometric enhancement for scintillation modeling

Continuous improvement of scintillation models is an important task required for adequate analysis and prediction of scintillation events caused by ionospheric irregularities. Some improvement can be achieved by an improved geometric description of small-scale perturbations in the ionosphere. Recently we revise the classical results of Ref. [1] obtained in the flat-earth approximation and generalized them for the case when the finite curvature of the earth has to be considered. Assuming that the earth is spherical, we obtained the analytic expressions for phase and intensity scintillation indices [2] in the approximation of a single thin phase changing screen. Figure 1 illustrates the difference between to mentioned geometries that becomes especially apparent at large zenith angles of the ground-based observer. The obtained results for spherical-earth geometry are divergence-free and represent the appropriate position of the enhancement maximum as a function of the dip angle for field-aligned ionospheric irregularities. Thus, the spherical-earth model is suitable for scintillation modeling and forecasting in such user cases as limb sounding, reflectometry, positioning at small elevation angles. Implementation of the proposed geometric considerations in the Global Ionospheric Scintillation Model is also briefly discussed. 1 C. L. Rino, "A power law phase screen model for ionospheric scintillation: 1. Weak scatter," Radio Sci., 14, November 1979, pp. 1135-1145, doi: 10.1029/RS014i006p01135 2 D.V. Vasylyev, Y. Bèniguel, M. Kriegel, V. Wilken, J. Berdermann, "Modeling ionospheric scintillation," JSWSC, 12, 22 June 2022 doi: 10.1051/swsc/202201

Global Ionospheric Scintillation Model: current status and further development strategies

When a electromagnetic wave propagates through a random inhomogeneous medium, scattering by the refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study and modelling. The Global Ionospheric Scintillation Model (GISM) is primarily intended to model the phenomena relevant for the GNSS applications and provides the amplitude and phase scintillation indices. Due to the three dimensional nature of the GISM model it is capable to describe a variety of communication geometries such as satellite-ground station or satellite-satellite communication link. Moreover, it can calculate the scintillation maps at specific altitude allowing to obtain the 3D picture of scintillation. Recently the GISM model has been handed over to the newly established DLR Institute of Solar-Terrestrial Physics. Since then the model underwent several modernization steps. For example, the programming paradigm has been changed to the object-oriented one in order to bring more flexibility into the code. In the present contribution we present the first results of our works and discuss strategies for further development, extension, and validation of the GISM