Перегляд за автором "Gnatenko, A. S."
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Публікація Airy Pulse Transformation by an Accelerated Medium Boundary(CAOL, 2019) Zhyla, O. V.; Nerukh, A. G.; Gnatenko, A. S.In the statement of a problem with a moving boundary there is one more idealization, namely, movement stationarity assuming that the movement has begun at infinite past time. Abandoning this idealization, by considering a movement that begins at a finite moment of time, leads to the appearance of new peculiarities in the wave transformation on a moving boundary. In this paper such peculiarities are considered with an abrupt uniform movement of a boundary beginning at zero moment of time, as well as with a smooth “turning on” of a boundary movement according to a relativistic uniformly accelerated law. In the latter approach the continuity of a boundary velocity change allows the development of the evolution of the wave transformation process to be traced.Публікація Airy Pulse Transformation by an Accelerated Medium Boundary(CAOL, 2019) Gnatenko, A. S.; Zhyla, O. V.; Nerukh, A. G.In the statement of a problem with a moving boundary there is one more idealization, namely, movement stationarity assuming that the movement has begun at infinite past time. Abandoning this idealization, by considering a movement that begins at a finite moment of time, leads to the appearance of new peculiarities in the wave transformation on a moving boundary. In this paper such peculiarities are considered with an abrupt uniform movement of a boundary beginning at zero moment of time, as well as with a smooth "turning on" of a boundary movement according to a relativistic uniformly accelerated law. In the latter approach the continuity of a boundary velocity change allows the development of the evolution of the wave transformation process to be traced.Публікація Femtosecond fiber laser for hair removal(Університет ім.Т.Г.Шевченка, 2015) Gnatenko, A. S.; Aleksieieva, K. D.; Vasko, К. А.Публікація Generation mode stability of a fiber ring laser(Begell House, 2015) Gnatenko, A. S.; Machekhin, Yu. P.To provide DWDM systems with a single source of radiation, it is possible to use a fiber femtosecond laser operating in the mode of generation supercontinuum. Functioning of a fiber ring laser operating in the mode of a train of ultra-short pulses is determined by the presence of liquid crystal polarizers being part of the resonator. Understanding of the control mode conception for passive mode locking by means of the liquid crystal polarizers is possible upon stable laser operating conditions. Therefore, it is purposed to study the conditions of sustainable modes of the ultra-short pulse fiber ring laser.Публікація Laser anemometry method for particle velocity measurement in the bose-Einstein condensate(Begell House, 2018) Machekhin, Yu. P.; Kurskoy, Yu. S.; Gnatenko, A. S.Studying of physical and engineering conditions of the process of atom velocity measurement in Bose-Einstein condensate is performed in the paper. In order to provide for the metrological support of the particle laser cooling process it is suggested the laser anemometry method based on measuring the Doppler frequency shift due to scattering of laser radiation by the moving particles to be cooled. The laser anemometry method for estimation of the particle velocity during the particle laser cooling process and the interferential model of the laser Doppler anemometry are provided. The requirements set to technical specifications of the laser Doppler anemometer are determined. The results of the paper form the basis of providing for the metrological support of the particle laser cooling process performed in order to create new frequency standards, the Bose-Einstein condensate and the quantum memory.Публікація Mode locking in a fiber femtosecond laser using liquid crystal cells(YSF, 2015) Gnatenko, A. S.; Vasko, К. А.In this paper, we present the configuration of erbium-doped fiber laser. The laser operates in passive mode locking. Usually in existing schemes fiber ring laser using mechanical adjustment mode locking by rotating in the space of the wave plates. In our optical system, we propose to use voltagecontrolled liquid crystal cells, to replace conventional polarization controllers (quarter-half-wave plate) inside the laser cavity. Using this innovation, freed from the mechanical adjustment mode locking, we plan to obtain the pulse width of the order of hundreds femseconds and an average power output of the order of tens milliwatts.Публікація Multiple Plane Waves Expansion Method for Dispersive Media(Begell House, 2008) Guryev, I. V.; Sukhoivanov, I. A.; Gnatenko, A. S.; Lipkina, V. I.This paper presents the multiple plane waves expansion method. The method is based on plane waves expansion technique but it oriented primarily to the computation of band structures of photonic crystals containing dispersive materials. The verification of the method is also given in the work by comparison of results obtained for the same photonic crystal by multiple plane waves expansion method and by the finite difference time domain method with recursive convolution. Results obtained in the work show high accuracy of the method as well as its high performance and universality.Публікація Nanolaser superradiation in information and measuring procedures(Begell House, 2018) Machekhin, Yu. P.; Kurskoy, Yu. S.; Gnatenko, A. S.; Tkachenko, V. A.The subject of the paper is superradiance of nanolasers and its process of quantum dot formation, increased concentration of non-equilibrium charge carriers, as well as physical principles of nanolasers operation with superradiance in telecommunication systems. The objective of the paper is to substantiate the possibility of using nanoscale lasers in the superradiance mode and the devices on their basis to solve problems of transmission of high- speed optical information signals and tasks of the radiation frequency stabilization. Review of several types of nanolasers is performed. It is determined that despite the creation of a number of designs, a general theory of stabilizing the parameters of nanolaser radiation is not developed. It is a deterrent to the development of this type of lasers and their practical application. To use nanolasers in information-measuring procedures, the problems of stabilizing the radiation frequency, obtaining pulses of a predetermined duration (of the femtosecond order), and the peak power must be solved. To provide pulsed radiation with the necessary parameters, the authors propose to use the superradiance mode previously discovered in semiconductor heterostructures and expressed in a sharp increase in the radiation power. The analysis of the conditions for the formation of superradiance in the domain structure of semiconductors is based on the theoretical model for describing the concentration of non- equilibrium carriers (electrons and holes) in the active region of the laser. The process of occurrence of superradiance in nanolasers and the possibility of using this effect are considered. It is proved that high-power femtosecond pulses are formed in nanolasers with superradiance. The results of the carry out studies substantiate the possibility and prospect of using nanolasers in the mode of superradiance and the devices on their basis for transmission of high-speed optic information signals, creation of new optical frequency standards and photonics devices. Their application will contribute to the development of nanometrology, nanotechnology, information and other technologies. Calculations are performed to prove that in the superradiance mode, nanolasers generate the femtosecond pulses with a power of 10.9 μW, which allows the signal to be transmitted along the optic fiber to the distance of 750 m. In the future, works are planned to increase the power of such lasers to transmit information for the longer distances.Публікація Optimization of thermal regime of continuous co2-lasers with diffusion cooling(Begell House, 2018) Vasyanovich, A. V.; Gnatenko, A. S.; Pustylnikov, D. V.Mathematical methods for optimizing parameters of the CO2-laser, realized using numerical computer simulation, are proposed. The results of numerical calculations coincide with the results of the experimental data, at a partial discrepancy, the reasons associated with the non- optimal consideration of the proposed recombination model on the wall of the O-tube. The results of the work can be fully used to optimize various designs of continuous CO2-lasers.Публікація Photonic crystal nanolasers as optical frequency standards(Begell House, 2018) Machekhin, Yu. P.; Gnatenko, A. S.; Kurskoy, Yu. S.Using of the nanolasers with the system of radiation frequency stabilization for development of the nano-size order optical frequency standards is considered in this paper. A number of nanolaser designs, their radiation processes and frequency stabilization are examined. The quantum dot nanolaser model with the wavelength of λ = 633 nm is developed. Radiation frequency stabilization is performed with the help of the iodine molecules placed into the photonic crystal cell having the T-shaped defect.Публікація Physical and mathematical foundations of measurements in nonlinear dynamic systems(Begell House, 2018) Machekhin, Yu. P.; Kurskoy, Yu. S.; Gnatenko, A. S.Physical and mathematical bases of measurements in physical non-linear dynamical systems are formulated. Physical properties, common to different systems, include: interval physical values; different modes of dynamics (including chaotic); strong dependence on the initial conditions; exposure to noise. We have used mathematical tools and methods of the dynamic chaos theory, open systems theory, fractal analysis: intervals of quantities values, fractal dimension, predictability time, model equation and others. New results and models are important for creating lasers with high stabilization of characteristics and practical application of solitons.Публікація Providing control of the polarization inside the resonator fiber ring laser(ВПЦ "Київський університет", 2015) Gnatenko, A. S.; Machekhin, Yu. P.; Vasko, K. O.This paper presents the implementation of the mode-locked fiber laser ring by nonlinear rotation polarization (NPR). This method is implemented using liquid crystal (LC) cells, which control the polarization of laser light by applying them an alternating signal. It was also conducted experiments of the interaction of laser radiation (wavelength 1550 nm) from the LC cell. It was built and research diagrams the stability of the polarization in the fiber ring laser.Публікація Ring fiber lasers for telecommunication systems(Begell House, 2018) Gnatenko, A. S.; Machekhin, Yu. P.; Kurskoy, Yu. S.; Obozna, V. P.; Vasianovych, A. V.The goal of this research is to study the interactions between a laser radiation and a liquidcrystal cell and to ensure the mode-locking in a ring fiber laser. In this paper we discuss how a non-linear polarization rotation in ring fiber lasers can be used to achieve the mode-locking. By supplying voltage to a liquid-crystal cell, we studied the polarization behavior both in theory and through experiment. Optical circuit of the ring fiber laser has been suggested.Публікація The study polarization control using the lc cells inside the resonator of a fiber femtosecond laser(Університет ім.Т.Г.Шевченка, 2015) Gnatenko, A. S.; Vasko, К. А.; Aleksieieva, K. D.In this article reviewed the implementation of lasing in the fiber ring laser.Публікація Topological methods in measurement and research of nonlinear dynamical systems(ХНУ, 2018) Kurskoy, Yu. S.; Machekhin, Yu. P.; Gnatenko, A. S.The authors substantiate the need to create a special theory of measurement and analysis of measurement results for nonlinear dynamical systems. The theory should be based on the principles of the open systems theory, dynamic chaos theory and synergetics theory. The authors analyzed the main topological methods and tools for studying of nonlinear dynamic systems. The main characteristics of nonlinear dynamical systems (interval values of dynamic variables, strong dependence on initial conditions and noise, complex, often chaotic dynamics, evolution) were systematized. It was proposed the next topological tools for analysis of measurement results in nonlinear dynamical systems: measurement portrait, Shennon entropy, fractal dimension, forecasting time.