Optoelectronics, Instrumentation and Data Processing (v.54, #2)

Laser Technologies in Micro-Optics. Part 2. Fabrication of Elements with a Three-Dimensional Profile by A. G. Poleshchuk; V. P. Korolkov; V. P. Veiko; R. A. Zakoldaev; M. M. Sergeev (113-126).
Recent research in the field of formation of a 3D profile of optical elements with the use of direct laser 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.
Keywords: micro-optics; direct laser writing; gray-scale photolithography; half-tone method; microplasma

Formation of Thick High-Aspect-Ratio Resistive Masks by the Contact Photolithography Method by A. N. Gentselev; F. N. Dul’tsev; V. I. Kondrat’ev; A. G. Lemzyakov (127-134).
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 patterns for LIGA masks, stamp microrelief, cast moulds, etc. Specific features of the contact photolithography method, which is used to design and fabricate the research device, are described. A source of exposure radiation in this device is a light-emitting diode. A possibility of obtaining individual elements of the resistive mask (in particular, with the lateral size ~5 μm, height of ~70 μm, and aspect ratio of ~14) and also the titanium stamp microrelief (with the height up to ~40 μm) generated by means of reactive ion-beam etching through the resistive mask, is experimentally demonstrated.
Keywords: deep contact photolithography; contact photolithography device; SU-8 resist; LIGA masks; stamp or cast mould microrelief

High-order reflexes on volume reflection holographic gratings in a photopolymer material are experimentally detected.
Keywords: volume holograms; Bragg diffraction; reflection gratings; photopolymers

Results of the development and testing of a device for detecting and analyzing the diffraction pattern of computer-generated holograms are reported. It is demonstrated that this device allows characterization 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 ±90° and 360° in terms of the azimuthal angle. A possibility of determining the periods, duty cycle, 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 computer-generated holograms in the course of their fabrication.
Keywords: diffraction optics; computer-generated holograms; computer optics; image processing; measurement systems

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 mismatch and quasioptimal algorithms, which are capable of operating in arbitrary mismatches between measured parameters and their estimates in the case of random signal/noise ratio at the gauge input. This work also presents the obtained 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 discrimination characteristic, and the value of the phase characteristic in the domain of small mismatches. 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 a closed servo-system.
Keywords: nonlinear transformation unit; nonlinear processing efficiency; amplitude and phase characteristics of the discriminator; signal/noise ratio

Nonlinear Filter Model for Digital Imaging of Contrast Images by V. A. Surin; A. N. Tyrsin (155-161).
This paper describes a model of digital filtering of noisy contrasting images with minimum blur of brightness at the overfall boundary, which is based on smoothing out digital images with the help of the generalized method of least absolute values. The model requires 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 Monte Carlo statistical test method.
Keywords: contrast image; digital filtering; model; aperture; generalized method of least absolute values

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.
Keywords: stealth radar; combined detection and localization of echoes; radio image

Spectroscopy of Single AlInAs Quantum Dots by I. A. Derebezov; A. V. Gaisler; V. A. Gaisler; D. V. Dmitriev; A. I. Toropov; A. S. Kozhukhov; D. V. Shcheglov; A. V. Latyshev; A. L. Aseev (168-174).
A system of quantum dots based on Al x In1−x As/Al y Ga1−y As solid solutions is investigated. The use of Al x In1−x As wide-gap solid solutions as the basis of quantum dots substantially extends the spectral emission range 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 In1−x As single quantum dots grown by the Stranski–Krastanov mechanism were studied by cryogenic microphotoluminescence. The statistics of the emission of single quantum dot excitons was studied using a Hanbury Brown–Twiss interferometer. The pair photon correlation function indicates the sub-Poissonian nature of the emission statistics, which directly confirms the possibility of developing single-photon emitters based on Al x In1−x As quantum dots. The fine structure of quantum dot exciton states was investigated at wavelengths near 770 nm. The splitting of the exciton states is found to be similar to the natural width of exciton lines, which is of great interest for the development of entangled photon pair emitters based on Al x In1−x As quantum dots.
Keywords: semiconductor quantum dots; exciton; biexciton; fine structure of exciton states; sub-Poissonian statistics; single photon emitters; polarization-entangled photon pair emitters

Experimental Investigation of a Piezo-Optical Transducer for Highly Sensitive Strain Gauges by A. G. Paulish; P. S. Zagubisalo; V. N. Barakov; M. A. Pavlov (175-180).
The characteristics of a piezo-optical transducer of a new design with high strain sensitivity at compact size have been studied.The original form of the photoelastic element provides a considerable increase in the stress in its working area at a given external force, resulting in an increase in the sensitivity of the transducer. The main characteristics of the transducer were measured using a specially designed device. The strain at a given applied force was calculated using a developed mathematical model of the transducer. As a result, the sensitivity to the relative strain was Δx/x=3 · 10−10, the dynamic range was at least four orders of magnitude higher and the gauge factor three orders of magnitude higher than those of strain-resistive gauges.
Keywords: strain measurement; strain gauges; piezo-optical transducer; photoelasticity method; optical methods for studying stress states

Influence of a Low-Temperature GaAs Dislocation Filter on the Perfection of GaAs/Si Layers by D. S. Abramkin; M. O. Petrushkov; E. A. Emel’yanov; M. A. Putyato; B. R. Semyagin; A. V. Vasev; M. Yu. Esin; I. D. Loshkarev; A. K. Gutakovskii; V. V. Preobrazhenskii; T. S. Shamirzaev (181-186).
The influence of dislocation filters based on low-temperature layers (LT) of GaAs and postgrowth annealing on the perfection of GaAs/Si heterostructures is discussed. It is shown that LT-GaAs layers reduce the density of threading dislocations and surface roughness. Post-growth annealing at a temperature of 650 °C reduces the concentration of nonradiative recombination centers in GaAs/Si layers to a level close to the level in GaAs layers grown on a matched substrate.
Keywords: epitaxy; low-temperature GaAs; dislocation filter

Multi-junction solar cells based on III–V compounds are the most efficient converters of solar energy to electricity and are widely used in space solar arrays and terrestrial photovoltaic modules with sunlight concentrators. All modern high-efficiency III–V solar cells are based on the long-developed triple-junction III–V GaInP/GaInAs/Ge heterostructure and have an almost limiting efficiency for a given architecture — 30 and 41.6% for space and terrestrial concentrated radiations, respectively. Currently, an increase in efficiency is achieved by converting from the 3-junction to the more efficient 4-, 5-, and even 6-junction III–V architectures: growth technologies and methods of post-growth treatment of structures have been developed, new materials with optimal bandgaps have been designed, and crystallographic parameters have been improved. In this review, we consider recent achievements and prospects for the main directions of research and improvement of 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 sunlight. It is supposed that by 2020, the efficiency will approach 40% for direct space radiation and 50% for concentrated terrestrial solar radiation. This review considers the architecture and technologies of solar cells with record-breaking 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 sunlight concentrators.
Keywords: architectures and technologies of III–V solar cells; III–V/Si solar cells; III–V/Si-Ge-Sn solar cells; multi-junction solar cells; subcells; metamorphic layers

A method of amplification and shaping of analog signals produced by a large-capacitance signal source is proposed. This method is optimized for reaching the highest signal/noise ratio, and, along with that, it allows for recognizing signals that arrive with a small time interval. An amplifying channel is designed that implements the proposed method. This channel is purposed for amplification of avalanche photodiode signals in detectors based of fast scintillators. The structure of the amplifying channel, the principle of recovering the shape of the input signal, and the basic circuit design solutions used in the developed amplifier are described.
Keywords: signal amplifiers; avalanche photodiodes

In modern high-energy physics experiments, particular attention is paid to the global integration of information and computing resources into a unified system for efficient storage and processing of experimental data. Annually, the ATLAS experiment performed at the Large Hadron Collider at the European Organization for Nuclear Research (CERN) produces tens of petabytes raw data from the recording electronics and several petabytes of data from the simulation system. For processing and storage of such super-large volumes of data, the computing model of the ATLAS experiment is based on heterogeneous geographically distributed computing environment, which includes the worldwide LHC computing grid (WLCG) infrastructure and is able to meet the requirements of the experiment for processing huge data sets and provide a high degree of their accessibility (hundreds of petabytes). The paper considers the ATLAS grid information system (AGIS) used by the ATLAS collaboration to describe the topology and resources of the computing infrastructure, to configure and connect the high-level software systems of computer centers, to describe and store all possible parameters, control, configuration, and other auxiliary information required for the effective operation of the ATLAS distributed computing applications and services. The role of the AGIS system in the development of a unified description of the computing resources provided by grid sites, supercomputer centers, and cloud computing into a consistent information model for the ATLAS experiment is outlined. This approach has allowed the collaboration to extend the computing capabilities of the WLCG project and integrate the supercomputers and cloud computing platforms into the software components of the production and distributed analysis workload management system (PanDA, ATLAS).
Keywords: distributed computing; information systems; grid middleware; integration of computing resources