Continuous-wave lasing of single-mode metamorphic quantum dot lasers for the 1.5-μm spectral region

Lasers based on InAs/InGaAs quantum dots grown on metamorphic (In,Ga,Al)As layers deposited by MBE on GaAs substrates exhibited emission near 1.5 μm with a differential quantum efficiency of about 50%. The narrow-stripe lasers operate in a single transverse mode and withstand continuous current density above 20 kA cm^?2 without significant degradation. A maximum continuous-wave output power of 220 mW is obtained. Neither current nor beam filamentation was observed up to the highest pumping levels.     

Solution of the stochastic H ∞-optimization problem for discrete time linear systems under parametric uncertainty

The stochastic H _∞-optimization problem for a linear discrete time system with uncertain parameters is formulated and solved. The system operates in the presence of Gaussian random disturbances. The original problem with parametric uncertainty is reduced to the stochastic H _∞-optimization problem without uncertainty and having one extra input, which is essentially the mixed H ₂/H _∞-optimization problem. In a sense, the problem considered in this paper incorporates the classical H ₂/H _∞-and H _∞-optimization problems as limiting cases.     

High-frequency electrical properties of a vertical-cavity surface-emitting laser with a monolithically integrated electro-optical modulator

The high-frequency electrical properties of a vertical-cavity surface-emitting laser with a monolithically integrated electro-optical modulator are studied using small-signal modulation analysis of the electroreflectance. The experimental data obtained are approximated using the suggested equivalent electrical circuit, which accounts for the formation of a nonequilibrium space charge in the carrier-depletion region of the modulator. The bandwidth of the high-frequency electrical-signal transfer to the electro-optical region, determined for the suggested equivalent electrical circuit of the modulator, is shown to be 3GHz.     

Influence of the position of InGaAs quantum dot array on the spectral characteristics of AlGaAs/GaAs photovoltaic converters

Results of a comparative study of the internal quantum yield of AlGaAs/GaAs photovoltaic converters (PVCs) with variable position of the array of vertically coupled InGaAs quantum dots (QDs) are presented. It is established that the QD array placed immediately at the i-region/base interface does not change the PVC sensitivity compared to that for QDs arranged inside the i-region of the p-n junction. However, the QD array shifted to the base or the back potential barrier decreases the contribution of a base layer to the PVC photocurrent and reduces the photosensitivity of the QD-based medium.     

Synthesis of ZnO-based nanostructures for heterostructure photovoltaic cells

A model describing heterostructure solar cells based on zinc and copper oxides is developed. Seed layers of ZnO and CuO are synthesized by spray pyrolysis. To form a bulk heterojunction, ZnO nanorods are grown by hydrothermal synthesis. The morphological, electricaland optical properties of the fabricated structures are investigated.     

Computational method for investigation of solid fuel combustion in combustion chambers of a heat power plant

Solid fuel combustion in an actual combustion chamber using coal with an ash content of more than 40% for minimization of the deleterious effects (environmental pollution) of heat power plants on environment. The FLOREAN application package was used for simulation and determination of various parameters of combustion.     

Startup of the Proton Radiographic Facility at the U-70 accelerator

The first results of Proton Radiographic Facility operation on the beam with energies of 50–70 GeV extracted from the U-70 synchrotron at the Institute for High Energy Physics are presented. This facility is capable of forming proton radiographic images of samples with an optical thickness as large as 450 g/cm² and a field of view of 220 mm or more.     

Multiturn fast extraction of the proton beam from the U-70 synchrotron

A novel system for high-energy beam extraction from the U-70 proton synchrotron to the external beam transfer line (i.e., a multiturn fast extraction system) is described. The beam is forced into the first upstream ejection device—an electrostatic deflector—by means of fast dipole bump magnets with the field rise time of 50–100 μs (equivalent of 10–20 beam turns). The fast bump magnets and their power supplies are described. The first experimental results acquired during trial operation of the multiturn fast extraction system in 2014 are presented. From these results, it is apparent that the extracted beam parameters are close to those obtained with the available single-turn fast extraction system.     

Petroleum nanodiamonds: New in diamondoid naphthenes

Recent data on the detection of hydrocarbons with a diamond-like structure, diamondoids, in crude oils and other natural objects have been summarized, methods for their isolation and analysis have been considered, and their potential use has been discussed.     

Broad-area InAs/GaAs quantum dot lasers incorporating intermixed passive waveguide

InAs/GaAs quantum dot lasers incorporating passive waveguide created by post-growth intermixing processing have been studied. Emission wavelength of the passive section shows relative blueshift as high as 135 nm with respect to the emission wavelength of the active section. Intrinsic losses in the section formed by the intermixing are very small. Broad-area lasers with 100 mum stripe width incorporating intermixed section have demonstrated improvements in far-field pattern under both pulsed and continuous wave pumping current