Optoelectronics, Instrumentation and Data Processing (v.53, #2)
Spatio-temporal generation regimes in fiber laser systems (Review) by D. V. Churkin; S. K. Khorev; I. D. Vatnik (103-113).
This paper presents a new concept for the study of spatio-temporal generation regimes in which several time scales coexist in the radiation (one of which is related to the cavity 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 successive cavity round trips. It is shown that fiber lasers of various types, e.g., quasicontinuous lasers and passively and actively mode-locked pulsed lasers, have a variety of spatio-temporal generation regimes. The possibility of experimental detection of localized structures, including solitons, in fiber laser radiation is demonstrated. The prospects of the proposed approach are discussed.
Keywords: optical heterodyning; temporal dynamics; extreme events; solitons; lasing intensity
Evaluation of the maximum speed of layer-by-layer heterodyne analysis of light scattering characteristics in volume optical media by P. E. Tverdokhleb; Yu. A. Shchepetkin (114-122).
A method of layer-by-layer heterodyne analysis of volume optical media is described. The results of a theoretical evaluation, computer modeling, and experimental investigation of the dependence of the maximum speed of the analysis on the parameters of the optical circuit and medium are given. The effect of the analysis speed on the resolution of the method along the thickness of the optical medium and on the pattern 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. The obtained results are confirmed experimentally..
Keywords: collinear heterodyning; linear frequency modulation; optical Doppler tomography; resolution; scanning speed
Alignment of the writing beam with the diffractive structure rotation axis in synthesis of diffractive optical elements in a polar coordinate system by R. V. Shimanskii; A. G. Poleshchuk; V. P. Korolkov; V. V. Cherkashin (123-130).
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 workpiece 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.
Keywords: diffractive optical elements; laser writing; nanopositioning; determination of the optical workpiece rotation axis
Dynamics of the crystallization front induced by the temperature gradient at the upper boundary of a horizontal layer of a fluid by V. A. Arbuzov; E. V. Arbuzov; Yu. N. Dubnishchev; V. S. Berdnikov; O. S. Melekhina (131-135).
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 T1 < 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.
Keywords: optical diagnostics of flows; Hilbert optics; convection in the water–ice system; phase transition in a supercooled fluid; crystallization wave
Electronic structure of atoms information system: Current status and development trends by V. V. Kazakov; V. G. Kazakov; V. S. Kovalev; O. I. Meshkov; A. S. Yatsenko (136-144).
The Electronic Structure of Atoms information system for atomic spectroscopy is proposed. Information on the size and characteristics of the website database is given, and the database parameters are compared with the best world analogues. 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 Electronic Structure of Atoms information system to solve various research tasks, including the analysis of the electronic structure of atomic systems, and to prepare experts is discussed.
Keywords: information systems; databases; spectroscopy; visualization; Grotrian diagrams; comparative analysis
High-speed processing of phase images with parallel computations by S. V. Dvoinishnikov; V. G. Meledin; V. A. Pavlov (145-150).
An algorithm is proposed for processing phase images with the use of computing power of graphics processing units (GPUs) for 3D 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.
Keywords: phase triangulation, structured light, GPU
Nonlinear robust control system for an unsteady nonaffine dynamic plant with a delay by E. L. Eremin; E. A. Shelenok (151-158).
A problem of design of a robust controller for an unsteady nonaffine (in terms of the input) a priori uncertain dynamic plant is considered. The quality of the designed control system performance is illustrated through simulations.
Keywords: robust control; a priori uncertainty; nonaffine plant; nonstationary; hyperstability criterion; L-dissipativity
Detection of suspicious objects on the basis of analysis of human X-ray images by D. V. Svitov; V. A. Kulikov; V. P. Kosykh (159-164).
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 during statistical pattern formation. It is experimentally demonstrated that this approach ensures adequate approximation of the result of detection of suspicious objects by humans.
Keywords: bag-of-words; X-ray images; search for anomalies
Neural network classification of hyperspectral images on the basis of the Hilbert–Huang transform by E. S. Nezhevenko; A. S. Feoktistov; O. Yu. Dashevskii (165-170).
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 and principal components without involving spatial information as features. Radial-basis and complex neural networks are used for classification.
Keywords: classification; hyperspectral image; Hilbert–Huang transform; principal components; complex neural networks
Analysis of elevation interpolation methods for creating digital elevation models by A. I. Pavlova (171-177).
Interpolation methods for creating digital elevation models using geoinformation system data are considered. For this purpose, the best-known methods are analyzed: inverse distance weighting (IDW), the Krige (or kriging) method, ANUDEM, spline interpolation, the natural neighbor method, and the method based on the construction of a triangular irregular network (TIN) model). The modeling accuracy is estimated for the area 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 relief model created using the ArcGIS 10 geoinformation system shows that the best results are obtained using spline methods and inverse distance weighting.
Keywords: digital elevation model (DEM); geographic information systems (GIS); morphometric topographic analysis; interpolation; approximation
Hybrid microcavity for superminiature single quantum dot based emitters by V. A. Gaisler; I. A. Derebezov; A. V. Gaisler; D. V. Dmitriev; A. I. Toropov; S. Fischbach; A. Schlehahn; A. Kaganskiy; T. Heindel; S. Bounouar; S. Rodt; S. Reitzenstein (178-183).
This paper describes the development and implementation of a microcavity based on a semiconductor Bragg reflector and a microlens selectively positioned over a single (111) InGaAs quantum dot. The structure of the microcavity ensures effective pumping of quantum dots and high external quantum emission output efficiency. This microcavity can be used to create single photon emitters and emitters of entangled photon pairs based on single semiconductor quantum dots.
Keywords: semiconductor quantum dots; exciton; biexciton; microcavities; Purcell effect; single photon emitters; emitters of entangled photon pairs
Charge transport in thin hafnium and zirconium oxide films by D. R. Islamov; V. A. Gritsenko; A. Chin (184-189).
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 phonon assisted tunneling between traps. From the comparison of experimental current-voltage characteristics 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.
Keywords: amorphous films; insulator with high insulator permittivity; hafnium oxide; zirconium oxide; transport
Development of a high-voltage waveguide photodetector comprised of Schottky diodes and based on the Ge–Si structure with Ge quantum dots for portable thermophotovoltaic converters by N. A. Pakhanov; O. P. Pchelyakov; A. I. Yakimov; A. V. Voitsekhovskii (190-196).
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 °C, practically used in thermophotovoltaic converters. 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 °C). 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 superthin 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 thermophotovoltaic converters and fiber-optic data transmission systems at wavelengths corresponding to basic telecommunication standards (λ = 0.85, 1.3 and 1.55, 1.3, and 1.55 μm) on the basis of silicon technologies.
Keywords: thermophotovoltaic; Schottky diode; high-voltage photodetector; Ge–Si quantum dots
Stochastic simulation of electron-hole recombination in two-dimensional and three-dimensional inhomogeneous semiconductors. Part II. Simulation results by K. K. Sabelfeld; A. E. Kireeva (197-202).
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 automaton) and continuous (Monte Carlo method) approaches. The particle recombination kinetics in pure diffusion and diffusion with tunneling is studied. There is a certain difference revealed 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. The comparative analysis of the simulation characteristics determined via cellular automaton and continuous recombination models is carried out.
Keywords: recombination; semiconductor; diffusion; tunneling; stochastic simulation; cellular automaton