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The optical characteristics of vertical cylindrical micropillars with AlGaAs distributed Bragg reflectors and InAs/GaAs quantum dots, which are designed for the fabrication of single-photon sources, have been studied. The effect of parameters such as the inclination angle of sidewalls, partial oxidation of AlGaAs layers, and deviation of quantum dots from the central axis of a micropillar on the Purcell factor and the radiation extraction efficiency has been numerically simulated by the finite-difference time-domain method. The allowable ranges of the listed parameters have been determined for cylindrical vertical 920-nm micropillars. The comparison of the calculations performed with the refined refractive indices of the used materials at cryogenic temperatures with the measured characteristics of the fabricated micropillar structures has confirmed the adequacy of the used models.

THE PURPOSE. Increasing the efficiency and efficiency of power plants based on renewable energy sources should be carried out by improving technological, constructive, organizational, legal, technical and economic measures. Proposals are given for the development of approaches to assessing the efficiency of wind power plants based on the Savonius rotor. The design parameters are substantiated and a physical model is created for a comprehensive study and performance characteristics in laboratory conditions.METHODS. Based on the methods of physical and mathematical modeling of structures and profiles of wind turbine blades, the technical and economic indicators of various profiles of the blades of the Savonius rotor are determined.RESULTS. The theoretical substantiation of the design and various profiles of the blades of the Savonius rotor is carried out. On the basis of a comprehensive study of performance characteristics in laboratory conditions, the values of the wind energy efficiency coefficient, the rotation frequency of the wind wheel profile, and electric power were established.CONCLUSION. The results of the study can be applied to substantiate the widespread use and creation of wind power plants with a Savonius rotor to ensure high-quality and reliable power supply to remote consumers of electric energy, the creation of isolated power systems and the further development of alternative energy sources in the domestic electric power industry

Abstract The author of this article holds that the entry of Soviet troops into Afghanistan was used by the opponents of the Soviet Union both in the West and in Central Asia to revive pan-Turkic ideas and to present the Soviet Union as an opponent of Islam in all its manifestations. To a certain extent, this situation was based on a serious study of the history and current state of Islam abroad. Soviet Islamic studies turned out to be on the far periphery of scientific interests. In the context of the outbreak of the conflict, domestic Islamic studies were found to be catching up. Research did not support knowledge at the level necessary for making political decisions. Politicians did not listen to experts; on the contrary, scientists tried to guess what the government wanted to hear from them.

The sedimentary basins of the north-western Weddell Sea are characterized by a variety of contourite drifts. This study is aimed at their identification, spatial mapping and temporal evolution and based on the integration of a large amount of seismic data collected by different countries including the recent data of the Russian Antarctic Expedition. Most of the drifts in the region being studied are classified as separated, confined, plastered or sheeted. The chain of sediment wave fields is mapped in the western and northern Powell Basin. The earliest contourite drifts started to form in the Early Miocene or, possibly, in the Late Oligocene. The changes in the depositional pattern in the Middle Miocene and then in the Late Pliocene are thought to have resulted from successive intensification of the bottom currents.

Впервые в отечественной историографии анализируется русскоязычный перевод с турецкого (литературный вариант османского) рукописи статьи самарского имама Мухаммет-Фатыха Муртазина (1875–1938), направленной в редакцию печатного органа Народного управления религиозными делами мусульман Крыма (НУРДМК) – религиозно-просветительского журнала «Асрий мусульманлыкъ» («Современное мусульманство», издавался в Симферополе в 1924–1927 гг.). Статья под названием «Ислам и цивилизация» планировалась к размещению в № 13 за 1926 г., ее перевод был выполнен сотрудником восточного отдела полномочного представительства ОГПУ по Крыму и направлен для согласования текста в Восточный отдел ОГПУ. Рукопись Муртазина содержит в себе ряд реформистских идей, по существу, весьма лояльных текущему политическому моменту, призванных адаптировать исламскую традицию к требованиям нового времени. Однако статья не была допущена к печати ввиду стремления ее автора представить приоритет исламской цивилизации над европейским и американским миром, что, очевидно, не отвечало мировоззренческим установкам работников советских спецслужб. Исследование выполнено в русле изучения интеллектуальной истории: представляя обзор сходных по содержанию статей крымского журнала, авторы обращают внимание на ход и характер напряженной богословской дискуссии и развитие «обновленческой» мысли в мусульманской среде Советского Союза 1920-х гг., дискуссии, протекавшей в условиях цензуры и зарождающегося идеологического прессинга.

—We discuss the structure of the Earth’s crust the seismic stratigraphy, thermal evolution, and stretching of the lithosphere in the sedimentary basin of the Cooperation Sea located on the continental margin of Antarctica in the south of the Indian Ocean. The sedimentary basin includes intracontinental and marginal rifts; the former is located on the shelf, and the latter, in the deep-water area. A seismostratigraphic analysis has revealed four sequences in the sedimentary cover of the intracontinental rift, which formed from middle Permian to late Cenozoic, and nine sequences in the sedimentary cover of the marginal rift, which have been deposited since the Middle Jurassic. One-dimensional numerical modeling of the thermal regime and the basement subsidence was performed over 18 points along the profile crossing the basin from the shelf to the lower continental rise. Based on the results of modeling and seismostratigraphic analysis, we have established variations in rock temperature with depth and in the degree of lithosphere stretching throughout the basin rift history. The modeling showed that the depth of the basement subsidence and the thickness of the crystalline part of the basin crust are governed by the lithosphere stretching before sedimentation. The maximum stretching is reached at the depocenters of rift structures (where the crust is the thinnest), being 2.8 before sedimentation and 1.16 after it in the intracontinental rift and 4.6 and 1.4, respectively, in the marginal rift.

This paper considers crustal structure, seismic stratigraphy, thermal evolution and lithospheric stretching of the deep-water basin located on the East Antarctic passive margin in the Princess Elizabeth Trough. Seven of the Middle Jurassic to Quaternary seismic sequences was identified based on interpretation of multichannel seismic data. The information about seismic stratigraphy and crustal thickness (calculated from gravity data) along the section crossing the Princess Elizabeth Trough was used for numerical modeling of the thermal regime of the lithosphere, tectonic subsidence of the crystalline basement and lithospheric stretching. Modeling shows that calculated tectonic subsidence is possible only under the assumption of crustal extension before the deposition (during the crustal doming at the early rift phase). Maximum stretching factor in the basin ranges from 1.1 to 2.0 for the period which preceded the deposition and 2.8 for the period of the rift-related deposition.

We describe the growth, material characterization, and lasing of InP/GaInP quantum dot (QD) microdisks (diameter D = 2.2 [Formula: see text]m, quality factor [Formula: see text]) with an emission lasing line of 693 nm (77 K). We demonstrate that MOVPE growth can result in two types of InP/GaInP QDs, differing in height (type A [Formula: see text]–10 nm, type B [Formula: see text] nm), whose emission has different decay lifetimes ([Formula: see text] ns, [Formula: see text] ns). We show, importantly for technological microlasing applications, that lasing occurs via the excited states of type A QDs, as inferred from a number of experimental results: power-dependent photoluminescence, time-resolved experiments, and temperature dependence of the generation threshold.

We demonstrate a record low threshold current density of 250 A/cm2 in a quantum dot microdisk laser with a 31-μm diameter operating at room temperature in continuous wave regime without temperature stabilization. This low threshold current density is very close to the transparency current density estimated in broad-area edge-emitting lasers made of the same epitaxial wafer.

Optimum shape of the capacitance–voltage (C–V) characteristic is a critical parameter determining the efficiency of frequency multiplication in heterobarrier varactors (HBVs) operating in the millimeter and submillimeter frequency ranges. A numerical model for calculating the C–V characteristics and leakage currents of HBV heterostructures with arbitrary composition and doping profiles has been verified on the basis of published and original experimental data. A specially designed HBV heterostructure with three undoped InAlAs/AlAs/InAlAs barriers surrounded by nonuniformly doped n-InGaAs modulation layers has been grown by molecular beam epitaxy on InP substrate. Prototype HBVs manufactured using the proposed heterostructure demonstrated a nearly cosine shape of the C–V curve at bias voltages up to 2 V, increased overlap capacitance, and low leakage currents.

Microdisk lasers 10–30 μm in diameter operating at room temperature without thermal stabilization and with an active region based on nanostructures of hybrid dimensionality—quantum wells–dots—are investigated. High-frequency measurements of the microlaser response are performed in the direct small-signal modulation mode, which makes it possible to establish the parameters of the operating speed and analyze their dependence on the microlaser diameter. It is found that the K factor is (0.8 ± 0.2) ns, which corresponds to optical losses of ~6 cm–1, and no regular dependence on the diameter is observed. It is found that the low-frequency component of the damping coefficient of relaxation oscillations is inversely proportional to the diameter. This character of the dependence evidences a decrease in the carrier lifetime in small-diameter microcavities, which can be associated with the prevalence of nonradiative recombination on their side walls.

The statistics of photon correlations in the emission of single InAs/AlGaAs quantum dots grown by molecular beam epitaxy and fitted with AlGaAs waveguide nanoantennas for efficient extraction of radiation is investigated. A single-photon source for the red spectral range with an average emission rate exceeding 5 MHz and a zero-delay second-order correlation function of g(2)(0) = 0.08 is realized on the basis of these photonic nanostructures. The degree of indistinguishability of consecutively emitted photons measured in Hong-Ou-Mandel interferometry under above-barrier excitation is about 30%.

A post-growth technique aimed at spatial modification of facet reflectance of edge-emitting diode lasers has been proposed. It is based on the deposition of an anti-reflection coating and subsequent precise etching with a focused ion beam. The technique allowed suppressing of high-order lateral modes in 10 μm stripe lasers based on ten layers of InAs/InGaAs quantum dots.

GaInP microdisks contained InP/GaInP quantum dots having lateral size ∼150 nm and 1-5 μm−2 were investigated with help of microphotoluminescence technique. Experiments carried out in confocal, time-resolved and low-temperature modes. Comparison of results allowed to conclude that overlap of quantum dot emission area with whispering gallery mode antinode results in faster luminescence lifetime (Purcell effect). Whispering gallery mode lasing was detected. Obtained threshold power values were following 6 µW (Q=4500, T=8.5 K) and 0.4 µW (Q=7400, T=80 K).

A strip-loaded slot waveguide is used for collecting, confining, and guiding the emission of a microdisk laser with InAs/InGaAs/GaAs quantum dot (QD) active region operating in continuous wave mode under optical pumping. An analytical model was developed to determine the vertical coupling conditions between the microdisk laser and strip-loaded slot waveguide using the model of 5-layers horizontal planar structure. The scanning near-field optical microscope measurements performed on the 10-micron in diameter microdisk covered by a TiO 2 /SiO 2 /TiO 2 strip-loaded slot waveguide confirmed the mode coupling into and guiding along the loading strip.

In aquaculture, the efficiency of fish cultivation depends on the quality of water, its hydrochemical and microbiological indicators. Research in this area is short and insufficient. It is necessary to conduct a comprehensive study of water quality in various fish farming zones of the Russian Federation, including all the factors of pollution and self-purification of ponds, to prevent the transition of intensively used ponds to the category of hypereutrophic, to create conditions that stimulate the process of self-purification of water. The authors of this article studied the role of organisms that live in fresh and salty water for self-purification of ponds and the impact of fish-breeding processes on the hydrochemical and microbiological regime of water in fish farming, determined the water quality in the growing ponds of the branch of FSUE Natsrybresurs «Teplovsky Fish Nursery» with mono and polyculture. The obtained results update the information about the influence of pond fish farming on the regime of water reservoirs, in the future they will allow to make changes and maintain the ratio and vital activity of hydrobionts in the biocenosis of fish ponds at best possible level.

The burial history and thermal evolution of the lithosphere within the passive nonvolcanic Antarctic margin in the region of the Mawson Sea are numerically reconstructed for the margin areas along the seismic profile 5909 with the use of the GALO basin modeling system. The amplitudes of the lithosphere stretching at the different stages of continental rifting which took place from 160 to 90 Ma ago are calculated from the geophysical estimates of the thickness of the consolidated crust and the tectonic analysis of the variations in the thickness of the sedimentary cover and sea depths during the evolution of the basin. It is hypothesized that the formation of the recent sedimentary section sequence in the studied region of the Antarctic margin began ~140 Ma ago on a basement that was thinned by a factor of 1.6 to 4.5 during the first episode of margin stretching (160–140 Ma) under a fairly high heat flux. The reconstruction of the thermal regime of the lithosphere has shown that the mantle rocks could occur within the temperature interval of serpentinization and simultaneously within the time interval of lithospheric stretching (–160 < t

The studies of the emission linewidth for single-mode near-IR vertical-cavity surface-emitting lasers with an active region based on InGaAs/AlGaAs quantum wells and different optical microcavity design. For low mirror loss, lasers with a 1λ cavity and carrier injection through distributed Bragg reflectors demonstrate a linewidth of 70 MHz and its growth to 110 MHz with increasing mirror loss (corresponding differential of efficiency ∼0.65 W/A). The design of the optical cavity with carrier injection through intracavity contacts and low-Q composition Bragg lattices reduces the linewidth to 40 MHz in spite of high mirror loss (corresponding differential efficiency of ∼0.6 W/A).

In this paper, results are presented on III-V quantum well dot microring diode lasers tested at elevated temperatures. To the best of our knowledge, the first uncooled microdisk lasers with diameter of 40 μm with 3-dB bandwidth above 2 GHz at 55°C are demonstrated.

The molecular-beam epitaxy of InGaAs/InAlAs/AlAs structures for heterobarrier varactors is studied and optimized. The choice of the substrate-holder temperature, growth rate and III/V ratio in the synthesis of individual heterostructure regions, the thickness of AlAs inserts and barrier-layer quality are critical parameters to achieve the optimal characteristics of heterobarrier varactors. The proposed triple-barrier structures of heterobarrier varactors with thin InGaAs strained layers immediately adjacent to an InAlAs/AlAs/InAlAs heterobarrier, mismatched with respect to the InP lattice constant at an AlAs insert thickness of 2.5 nm, provides a leakage current density at the level of the best values for heterobarrier varactor structures with 12 barriers and an insert thickness of 3 nm.

We report a realization of room temperature lasing threshold of 1 μW in GaInP microdisk containing a few self-aggregated InP/GaInP quantum dots (QDs) grown by metal-organic vapor phase epitaxy. InP/GaInP QD microdisk cavities emitting in the spectral range of 700–800 nm and having the size of ~2 μm, free spectral range of ~35 nm and quality factors Q ~ 4000 were formed by wet chemical etching. Low dot density (~2 μm–2) and large dot size (~150 nm), suggesting a single dot lasing and maximum overlap of QD and cavity mode, were achieved using deposition of 3 ML of InP layer at 700°C.

We present an analysis of spectral and threshold characteristics of InGaAs/GaAs quantum well-dot microdisk laser operated under cw current injection at room temperature without external cooling. The experimental values of the threshold current for the disk and ring microlasers are compared. We observe that the threshold current can be significantly decreased in devices with large diameters (more than 30 μm) by using the ring geometry.

Studies aimed at optimization of the design of a dielectric distributed Bragg reflector (DBR) produced by the reactive magnetron sputtering method for applications in near-IR vertical-cavity surface-emitting lasers with intracavity contacts (ICC-VCSELs) are carried out. It is shown that the reflectivity of the dielectric DBRs based on SiO2/TiO2 decreases due to the polycrystalline structure of the TiO2 layers, which causes diffusive scattering of light. In contrast, amorphous Ta2O5 layers is characterized by a low surface roughness and low fluctuation in the refractive index. Single-mode ICC-VCSELs in the 980-nm spectral range with dielectric DBR based on SiO2/Ta2O5 with a threshold current less than 0.27 mA, electric resistance of less than 200 Ω, and differential efficiency of more than 0.8 W/A are demonstrated.

The polarization characteristics of 850-nm vertical-cavity surface-emitting lasers (VCSELs) with intracavity contacts and a rhomboidal oxide current aperture are studied. It is found that radiation polarization is always directed along the minor diagonal of the rhomboidal aperture (along the [ $$\overline 1 $$ 10] direction) for all single-mode VCSELs. The numerical simulation of carrier transport does not reveal the significant anisotropy of carrier injection to the active region. Furthermore, an analysis of the spatial distribution of the fundamental mode for two orthogonal polarizations within an effective waveguide model shows close transverse optical-confinement factors. Optical loss anisotropy in the asymmetric microcavity and/or gain anisotropy in the strained active region are the most likely mechanisms responsible for fixing the polarization.

Microdisk lasers based on three InGaAsN/GaAs quantum wells with different types of surface passivation are fabricated and studied under optical pumping. Room temperature lasing at 1.3 μm in 7 μm in diameter microdisks with InGaAsN/GaAs QW is demonstrated. We evaluated the thermal resistance as 1 °C/mW. publishedVersion

The dielectric permittivity tensor is analyzed qualitatively for the DNA nematic liquid crystal in the THz frequency range. The analysis is performed within the self-consistent phonon approximation based on the PBD model. It is found that DNA depolarization and absorption spectra depend on such parameters as molecular length and helix period. Specifically it is shown that a localization of the absorption lines in the frequency range is determined by the DNA helix structure whereas the DNA length is responsible for a separation between the absorption lines. It is also shown that the gyrotropic properties of the considered liquid crystal depend on a relation between the molecular length and its helix period. The molecules with even number of half helix periods demonstrate the strongest gyrotrophy whereas the molecules with odd number of half helix periods have the weakest gyrotrophy. The model is used to suggest the experimental methodology for determining the DNA length and helix structure based on measurements of the depolarization and absorption spectra in aqueous solutions of biopolimers. Methods of applied THz spectroscopy for determination of the conformational state of molecules in solution is announced. Some preliminary experimental results are presented, including details of measuring the absorption spectra of dry DNA sample and aqueous solutions of biopolimers.

The Southern Indian Ocean comprises large sedimentary basins of the Riiser-Larsen Sea (western sector); the Cosmonauts, Cooperation (Commonwealth), Davis seas (central sector); and the Mawson-d’Urville seas (eastern sector). The main tectonic provinces of the Southern Indian Ocean (Antarctica) have been outlined as a result of comprehensive interpretation of the geophysical data. Special attention is paid to determining the boundary between the rifted continental and oceanic crust. The basin of the Riiser-Larsen Sea was formed in the Early Jurassic under the action of the Karoo mantle plume. The intrusive complex, as a remote manifestation of the mantle plume, occurs along the inner boundary of the marginal rift. Opening of the ocean in the basin of Riiser-Larsen Sea started about 160 Ma ago and was characterized by rearrangement of plate motion and intense volcanic activity at the early stage. In the basin of the Cosmonauts, Cooperation, and Davis seas, the final stage of rifting was accompanied by the rise of the lithospheric mantle and by intrusive magmatism. The opening of the ocean started here 134 Ma ago. Emplacement of the Kerguelen plume resulted in jumping of ridges and detachment of continental crustal blocks from the Indian margin with the formation of the Kerguelen Plateau (microcontinent). The basin of the Mawson-d’Urville seas has evolved under conditions of long-term rifting since the Late Jurassic and is characterized by an extended zone of mantle unroofing. Breakup of the lithosphere between Australia and Antarctica developed asynchronously over a time interval of 95–65 Ma ago with propagation of MOR from the west eastward. The research was carried out using a great body of geophysical information (∼140000 km of CDP seismic profiling, more than 250 stations of seismic refraction sounding, and more than 250000 km of magnetic and gravity profiles) obtained by expeditions from many countries over more than 30 years.

The energy-to-data ratio (EDR) was evaluated for quantum-dot based microdisk laser directly modulated without external cooling. The experimental values of EDR decrease with decreasing diameter of the microdisk and reach 1.5 pJ/bit for the smallest diameter under study (10.5 μm). In larger microdisks (with a diameter greater than 20 μm), the EDR varies in proportion to the square of the diameter. If this relationship were true for smaller microdisks as well, an EDR value of about 100 fJ would be achieved with a diameter of 4 μm. The observed deviation of EDR from the quadratic dependence on the diameter is associated with an increase in the threshold current density in smaller devices, which in turn may be caused by the contribution of nonradiative recombination on the microresonator sidewalls formed by deep etching.The energy-to-data ratio (EDR) was evaluated for quantum-dot based microdisk laser directly modulated without external cooling. The experimental values of EDR decrease with decreasing diameter of the microdisk and reach 1.5 pJ/bit for the smallest diameter under study (10.5 μm). In larger microdisks (with a diameter greater than 20 μm), the EDR varies in proportion to the square of the diameter. If this relationship were true for smaller microdisks as well, an EDR value of about 100 fJ would be achieved with a diameter of 4 μm. The observed deviation of EDR from the quadratic dependence on the diameter is associated with an increase in the threshold current density in smaller devices, which in turn may be caused by the contribution of nonradiative recombination on the microresonator sidewalls formed by deep etching.

We report results of characterization of injection microdisk lasers based on active layers employing 2, 5 and 10 layers of InGaAs quantum well-dot structures. The microlasers operate in continuous wave regime at room temperature without external cooling. The minimal microdisk diameter 10 µm is obtained for 5 layers of InGaAs quantum well-dot structures. Lasing wavelength is around 1.1...1.15 µm, minimal threshold current is 1.6 mA (threshold current density 900 A/cm2).

Vertical-cavity surface-emitting lasers (VCSELs) are low-cost high-performance light sources for high-speed data communication systems, optical interconnects and different sensors [1]. New VCSEL applications (spectroscopy, compact atomic clock) require single-mode operation with stable linear polarization combined with high temperature stability. While conventional GaAs-based VCSELs with small selectively-oxidized current apertures demonstrate stable fundamental transverse mode operation they have unstable polarization due to cylindrical symmetry and isotropic gain. Currently the most popular method for VCSEL polarization control is based on precise etching of sub-wavelength grating in output distributed Bragg reflector [2]. Drawbacks of this approach are relatively complicated fabrication technology and limited output power. In this work we discuss alternative approach for single-mode polarization-stable VCSELs based on rhomboidal selectively-oxidized current aperture combined with intracavity contacts.

The possible mechanisms of the polarization control in single-mode intracavity- contacted vertical-cavity surface-emitting lasers (IC-VCSELs) with the rhomboidal selectively- oxidized current aperture were investigated. It was found that the lasing emission polarization of all single-mode VCSELs is fixed along the minor diagonal of the rhomboidal-shape aperture (the [110] direction). Numerical modelling of carrier transport did not reveal any sufficient injection anisotropy in the laser active region, while the transverse optical confinement factors calculated for the fundamental mode with two orthogonal polarizations are identical. Optical loss anisotropy and/or gain anisotropy are the most likely mechanisms of inducing the polarization fixation.

Optically pumped 3-6μm in diameters microdisk lasers with InGaAsN/GaAs quantum well active region has been studied. Single-mode CW lasing at 78K temperature in microdisk laser with 3 μm diameter is demonstrated.