Home – Home – Jornals – Avtometriya 2018 number 2

Recent research in the field of formation of 3D microrelief of optical elements with the use of direct laser beam writing at various wavelengths and photolithographic technologies on the basis of photomasks fabricated by means of laser writing is reviewed. Typical characteristics of the relief, as well as advantages and drawbacks of the above-mentioned methods are considered.

A method of fabrication of thick (~100 μm and more) resistive masks is described. These masks can be used for solving various engineering problems, e.g., for fabricating x-ray-absorbing topological pictures for LIGA templates, stamp microrelief, cast moulds, etc. Specific features of the contact photolithography method, which is used to design and fabricate a research setup, are described. A source of exposure radiation in this setup is a light-emitting diode. A possibility of obtaining individual elements of the resistive mask (in particular, with lateral sizes ~5 μm, height ~70 μm, and aspect ratio ~14) and also the titanium stamp microrelief (with height up to ~40 μm) generated by means of reactive ion-beam etching through the resistive mask, is experimentally demonstrated.

High-order reflexes in volume reflection holographic gratings in a photopolymer material are experimentally detected.

Results of the development and testing of a device for recording and analyzing the diffraction pattern of synthesized holograms are reported. It is demonstrated that this device allows recording of the diffraction pattern of radiation reflected from the surface microrelief of the considered element or transmitted through it in the angular range of diffraction of the order of ±90º and 360º in terms of the azimuthal angle. A possibility of determining the periods, duty ratio, and angular orientation of diffraction structures and also the diffraction efficiency of all diffraction orders of the examined element is described. The device is designed for real-time monitoring of the microrelief depth and shape of synthesized holograms in the course of their fabrication.

This paper describes the synthesis of algorithms for estimating signal information parameters with noninertial nonlinear transformation of the input mixture of the signal and broadband non-Gaussian noise. There is also the analysis of algorithms optimal in the domain of small detuning and quasioptimal algorithms, which are capable of operating in arbitrary detunings between measured parameters and their estimates in the case of random signal/noise ratio at the gauge input. Basic estimated relations that help one determine the form of optimal amplitude characteristics of the nonlinear transformation unit, the quality of suppression of additive noise in a given unit with optimal and arbitrary amplitude characteristic, the steepness of the discriminatory characteristic, and the value of the phase characteristic in the domain of small detunings. It is shown that, by specifying the type of action and the transfer function of a smoothing chain, it is possible to determine the steady-state dynamic and fluctuation errors in closed servo-system.

This paper describes a model of digital filtering of noisy contrasting images with minimum blur of brightness at the edge of the drop, which is based on smoothing out digital images with the help of generalized method of least modules. The model presupposes variation of two parameters of the loss function as a function on the degree of contrast and noise level. The results are based on extensive computational experiments performed by the method of Monte Carlo statistical tests.

This paper describes the results of experimental approbation of a computationally efficient procedure for constructing multidimensional (in the "angular direction - delay - Doppler frequency shift" coordinates) radio images of target echo signals by a variational method in radar complexes with extraneous illumination.

A system of quantum dots based on Al _x In_{1- x} As/Al _y Ga_{1- y} As solid solutions is investigated. Application of Al _x In_{1- x} As wide-gap solid solutions as the basis of quantum dots substantially expands the spectral range of the radiation to the short-wavelength region, including the wavelength region near ~770 nm, which is of interest for the development of aerospace systems of quantum cryptography. The optical characteristics of Al _x In_{1- x} As single quantum dots grown by the Stranski-Krastanov mechanism were studied by cryogenic microphotoluminescence. The statistics of radiation of the exciton states of single quantum dots was studied using a Hanbury Brown-Twiss interferometer. The function of paired photon correlations clearly shows the sub-Poissonian character of the radiation statistics, which directly confirms the possibility of developing single-photon emitters based on Al _x In_{1- x} As quantum dots. The fine structure of the exciton states of quantum dots was investigated in the wavelength region near ~770 nm. The magnitude of splitting of exciton states is found to be comparable with the natural width of exciton lines, which is of great interest for the development of emitters of pairs of entangled photons based on Al _x In_{1- x} As quantum dots.

The characteristics of a piezo-optical converter of a new design, which has small dimensions and high sensitivity to deformation. The original form of the photoelastic element makes it possible, at a given external force, to considerably increase the voltage in its working area, thereby increasing the sensitivity of the converter. The main characteristics of the converter were measured using a specially designed device. The developed mathematical model of the converter made it possible to calculate the strain at a given applied force. As a result, the sensitivity to the relative deformation was Δx/x = 3 x 10^-10, the dynamic range is more than four orders higher and the strain sensitivity coefficient is three orders of magnitude higher compared to strain-gauge sensors.

The influence of dislocation filters developed on the basis of low-temperature layers (LT) of GaAs and post-growth annealing on the perfection of GaAs/Si heterostructures is discussed. It is shown that LT-GaAs layers reduce the density of germinating dislocations and reduce the surface roughness. Post-hrowth annealing at a temperature of 650 ºC reduces the concentration of centers of nonradiative recombination in GaAs/Si layers to a level close to the level in GaAs layers grown on a matched substrate.

Multi-junctions solar cells (SCs) based on III-V compounds are the most effective converters of solar energy to electricity and are widely used in space solar batteries and ground photovoltaic modules with radiation concentrators. All modern high-performance III-V solar cells are based on the long-developed three-junction III-V heterostructure of GaInP/GaInAs/Ge and have practically limiting efficiency for this architecture 30 and 41.6 % for space and ground-based concentrated radiation, respectively. Currently, an increase in efficiency is achieved by changing over from 3-junction to more efficient 4-, 5-, and even 6-junction III-V architectures: growth technologies and methods of post-growth processing of structures have been developed, new materials with optimal forbidden zones) have been designed, and crystallographic parameters have been improved. The proposed review considers recent achievements and prospects for the main research areas and improvement of the architectures, technologies, and materials used in laboratories to develop solar cells with the best conversion efficiency: 35.8 % for space, 38.8 % for terrestrial, and 46.1 % for concentrated solar radiation. The physical properties of III-V compounds have been well studied and technologies for their production have been developed. The maximum efficiency of photoelectric conversion of SCs based on III-V heterostructures for extra-atmospheric solar radiation reaches 35.8 % [1], which determines their practical non-alternative use in space. In terrestrial conditions, the record efficiency of solar cells are 38.8 % for nonconcentrated (AM1.5G) and 46.0 % for concentrated (AM1.5D) radiations [1]. It is supposed that by 2020, the efficiency will approach 40 % for direct space radiation and 50 % for concentrated terrestrial solar radiation. This review reviews the architecture and technologies of solar cells with record-high efficiency for terrestrial and space applications. It should be noted that in terrestrial power plants, the use of III-V SCs is economically advantageous in systems with solar radiation concentrators.

This paper proposes a method for amplification and formation of an analog signal, optimized for reaching the larger signal/noise ratio in the operation with a large-capacity signal source and allowing for recognizing the signals that arrive with a small time interval. An amplifying channel is developed that implements the proposed method. This channel is designed to amplify avalanche photodiode signals in detectors based of fast scintillators. The structure of the amplifying channel, the principle of recovering the form of the input signal, and the basic circuitry solutions used in the developed amplifier are described.

In a modern experiment in the field of high-energy physics, special attention is paid to the global integration of information and computing resources into a single system for efficient storage and processing of experimental data. The ATLAS experiment conducted at the Large Hadron Collider European Organization for Nuclear Research annually produces tens of petabytes of data from the recording electronics, as well about one petabyte of data from the simulation system. For processing and storage of such super-large volumes of data, the computer model of the ATLAS experiment is based on the technology geographically distributed parallel computing, which includes the global grid infrastructure of the WLCG project (Worldwide LHC Computing Grid) and is able to meet the requirements of the experiment on processing huge data sets and provide a high degree of their accessibility (hundreds of petabytes). The paper considers the AGIS (ATLAS Grid Information System) central information system used by the ATLAS collaboration to describe the topology and resources of the computer infrastructure of the experiment, configure and connect the high-level software systems of computer centers, describe and store all possible parameters, control, configuration, and other supporting information required for the effective operation of the services of the global distributed processing system. The role of the AGIS system in the development of the concept of a general description of the resources of computing centers of grid nodes, supercomputer centers, and cloud computing resources in a single information model for the ATLAS experiment. This approach allowed the collaboration to expand the computing capabilities of the WLCG project and integrate supercomputers and cloud computing platforms into the software components of the production and distributed analysis workload management system (PanDA, ATLAS).