Home – Home – Jornals – Avtometriya 2017 number 2

This paper presents a new concept for studying the spatio-temporal modes of laser generation in which several time scales coexist in the emission (one of which is related to the resonator round-trip time). The essence of the concept is that the time dependence of the intensity is investigated in two dimensions, one of which corresponds to the evolution over sequential resonator round-trips. It is shown that fiber lasers of various types, e.g., quasicontinuous lasers and passive and active mode locked pulsed lasers, has a diversity of spatio-temporal generation modes. The possibility of experimental detection of localized structures, including solitons, in fiber laser radiation is demonstrated. The prospects of the proposed approach are discussed.

A method of layer-by-layer heterodyne analysis of volume optical media is described. The results of theoretical evaluation, computer modeling, and experimental investigation of the dependence of the maximum speed of analysis of the parameters of the optical circuit and medium are given. The effect of the analysis speed on the resolution of the method for the thickness of the optical medium and on the nature of the dependence of the output signal on the depth of the studied layer is evaluated. A method for increasing the maximum scanning speed is proposed. Results are confirmed experimentally.

A method is developed to ensure precise alignment of the origin of a polar coordinate system in which the laser beam position is defined in writing diffractive optical elements with the optical blank rotation axis. This method is used to improve the accuracy of a circular laser writing system in writing large-scale diffractive optical elements in a polar coordinate system. Results of studying new algorithms of detection and correction of positioning errors of the circular laser writing system in the course of writing are reported.

The dynamics of the crystallization front induced by the temperature gradient at the upper boundary of a horizontal layer of water bounded by flat thermostatted surfaces is studied. The formation and evolution of convective structures are visualized by methods of the Hilbert optics and digital video recording. The difference in the temperatures of the upper ( T₁) and lower ( T₂) thermostats satisfies the condition T ₁ < T₂. In this system, the temperature of the cooled upper surface is an order parameter. Reaching a critical value of this parameter leads to a bifurcation phase transition from the liquid state (supercooled water) to the solid state (ice). The velocity and shape of the crystallization wave front are determined. The spatial-temporal state of the crystallization wave is found, in which the wave front shape is a line of equal velocities. The dynamic profile of the isothermal surface bounding the spatial shape of the solid phase is visualized.

The information system "Electronic Structure of Atoms" for atomic spectroscopy is proposed. Information on the size and characteristics of the website data base is given, and the database parameters are compared with reputable world analogs. Scientific data visualization tools implemented in the form of spectrograms and Grotrian diagrams in the system are considered. It is shown that the classified levels and transitions in tabular and graphical forms are presented more fully than in similar information systems. The efficiency of using the information system "Electronic Structure of Atoms" to solve various research tasks, including the analysis of the electronic structure of atomic systems, and to prepare experts is discussed.

An algorithm is proposed for processing phase images with the use of computing power of graphics processing units (GPUs) for three-dimensional geometry measurements by means of phase triangulation. It is shown that implementation of the phase image decryption algorithm on the GPU is faster by more than 100 times than on the central processing unit (CPU). Practical implementation of the proposed approach can substantially improve the performance of phase triangulation methods.

A problem of construction of a robust regulator for a nonaffine nonstationary a priori uncertain dynamic object with a delay. The quality of operation of the constructed control system is illustrated through simulations.

A new approach is proposed for detection of suspicious objects in X-ray images for security assurance. The approach is based on using the statistical model of the image for detecting anomalies. The model is designed with the use of the "bag-of-words" with context definition of the word coordinates in the image in forming the statistical pattern. It is experimentally demonstrated that this approach ensures adequate approximation of the result of detection of suspicious objects by humans.

The method of image classification with its preliminary transformation to principal components and with the use of the Hilbert-Huang transform is studied by an example of neural network classification of a hyperspectral image. The efficiency of the method is demonstrated through comparisons with traditional methods of neural network classification with the use of spectral components as attributes and principal components without involving spatial information. Radial-basis and complex neural networks are used for classification.

Interpolation methods for developing digital terrain model using geoinformation system data are considered. For this purpose, the best-known methods are analyzed: inverse distance weighting (IDW), kriging, ANUDEM, spline interpolation, the natural neighbor method, and the method based on the construction of a triangulation irregular network (TIN) model). The modeling accuracy is estimated for a terrain located between the Ui, Tara, and Irtysh Rivers in the Omsk region of West Siberia (Russia). Analysis of the results of estimating the accuracy of a digital terrain model developed using the ArcGIS 10 geoinformation system shows that the best results were obtained using spline methods and inverse distance weighting.

This paper describes the development and implementation of a microresonator based on a semiconductor Bragg reflector and a microlens selectively positioned above a single InGaAs quantum dot (111). The microresonator constructor provides effective pumping of quantum dots and high external quantum radiation output efficiency. This microresonator can be used to create single-photon and photon-pair emitters entangled in polarization and based on single semiconductor quantum dots.

The mechanism of charge transport in MIS structures on the basis of thin hafnium and zirconium oxide films is studied. It is shown that transport in the studied materials is limited by photon facilitated tunneling between traps. From the comparison of experimental current-voltage caracteristics of MIS structures n -Si/HfO₂/Ni and n -Si/ZrO₂/Ni, the estimated, thermal, and optical energies of traps are determined. It is shown that oxygen vacancies are localization centers (traps) of charge carriers in HfO₂ and ZrO₂.

This paper demontstrates the possibility of developing a high-voltage waveguide photodetector comprised of Schottky diodes and based on a Au/Ge - Si structure with Ge quantum dots pseudomorphic to a silicon matrix, which ensures an increase in the external quantum yield and open-circuit voltage. It is shown on this photodetector that there is a great increase and broadening in sensitivity up to λ = 2.1 μm, which coincides with the main radiation range of a black (gray) body at the emitter temperatures from 1200 to 1700 ºC, practically used in thermal photogenerators. This state of the ensemble of Ge quantum dots by means of molecular beam epitaxy can be obtained only under the condition of low growth temperature (250-300 ^oC). It is established that, below the Si absorption edge, photoresponse on the photodetectors under consideration is determined by two main mechanisms: absorption on the ensemble of Ge quantum dots and Fowler emission. It is shown by the analysis of the Raman scattering spectra on the optical photons of Ge - Si structures that the quantum efficiency of photodetectors based on them in the first case is due to the degree of nonuniform stress relaxation in the array of Ge quantum dots. The photoresponse directly associated with the Ge quantum dots is manifested on Schottky diodes with a hyperfine intermediate oxide layer SiO2, which eliminates the second mechanism. In further development, the proposed photodetector architecture with pseudomorphic Ge quantum dots can be used both for portable thermal photogenerators and fiber-optic data transmission systems at wavelengths corresponding to basic telecommunication standards (λ = 0.85, 1.3, and 1.55 μm) on the basis of silicon technologies.

This paper describes the stochastic models of electron-hole recombination in inhomogeneous semiconductors in two-dimensional and three-dimensional cases, which were developed on the basis of discrete (cellular automation) and continuous (Monte Carlo method) approaches. The kinetics of the particle recombination in pure diffusion and diffusion with tunneling is studied. Certain difference between the behavior of electron-hole spatial correlations calculated by discrete and continuous models and the nature of segregation formation in three-dimensional semiconductors associated with that behavior is revealed. The comparative analysis of the simulation characteristics determined via cellular automatic and continuous recombination models is carried out.