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Pavel P Pashinin - One of the best experts on this subject based on the ideXlab platform.
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Polarisation of a Neodymium Laser with a passive switch based on a Cr4+ : YAG crystal
Quantum Electronics, 1998Co-Authors: Nikolai N Il'ichev, Alexander V. Kir'yanov, E S Gulyamova, Pavel P PashininAbstract:An experimental investigation is reported of the state of polarisation of the radiation generated in a Neodymium Laser with a passive switch based on a Cr4+ : YAG crystal. A description is provided of the observed dependences. This description is based on the assumption that at each moment of the evolution of lasing the state of polarisation of the Laser radiation represents an eigenstate corresponding to the lowest radiation losses. This state is governed by the relative orientations of the switch and of an intracavity partial polariser, as well as by the radiation energy density in the switch. The calculated results are shown to fit the experimental data.
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Passive Q switching of a Neodymium Laser by a Cr4+ : YAG crystal switch
Quantum Electronics, 1997Co-Authors: Nikolai N Il'ichev, E S Gulyamova, Pavel P PashininAbstract:Theoretical and experimental investigations were made of passive Q switching of a Neodymium Laser by a Cr4+ : YAG switch. Analytic expressions were derived for estimating the output energy of the TEM00 mode of a passively Q-switched Laser from the known parameters of the Cr4+ : YAG switch, of the active element, and of the cavity. The adopted description makes it possible to cover the range from generation of the first spike of a free-running transient to generation of a giant pulse. An experimental study was made of the dependence of the output energy on the cavity parameters, on the material of the active element (in this investigation it was Nd :YAG and Cr, Nd : GSGG), and on the angle of rotation of the Cr4+ : YAG switch. The experimental results obtained agreed to within 30% with calculations.
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Influence of the nonlinear anisotropy of absorption in a passive Cr4+ : YAG switch on the energy and polarisation characteristics of a Neodymium Laser
Quantum Electronics, 1997Co-Authors: Nikolai N Il'ichev, Alexander V. Kir'yanov, E S Gulyamova, Pavel P PashininAbstract:An experimental investigation was made of the polarisation characteristics of a solid-state Neodymium Laser with a passive Cr4+ : YAG switch. The energy and the state of polarisation of Laser radiation were affected radically by the orientation and position of the Cr4+ : YAG switch in the cavity, and also by the nature of an intracavity polariser. The polarisation characteristics of the Laser radiation were determined by a self-induced nonlinear-absorption anisotropy and a self-induced change in the state of polarisation of the Laser radiation during growth of a giant pulse when saturation of the absorption was 'switched on' in the Cr4+ : YAG crystal.
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An Influence of Passive Shutter Cr4+:YAG Latent Anisotropy on Output Energy and Polarisation Characteristics of Neodymium Laser at Passive Q-Switching
Advanced Solid State Lasers, 1997Co-Authors: Nikolai N Il'ichev, Alexander V. Kir'yanov, E S Gulyamova, Pavel P PashininAbstract:Nonlinear absorption anisotropy at the saturation stage in Cr4+ phototropic centers is shown to determine the angular dependencies of output energy and polarisation state of Neodymium Laser Q-switched with Cr4+:YAG crystal.
Nikolai N Il'ichev - One of the best experts on this subject based on the ideXlab platform.
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A polarisation-bistable Neodymium Laser with a Cr4+:YAG passive switch under the weak resonant signal control
Optics Communications, 1999Co-Authors: Alexander V. Kir'yanov, Vicente Aboites, Nikolai N Il'ichevAbstract:Abstract A polarisation-bistable device is proposed based on the phenomenon of dependence of polarisation state of a Nd:YAG Laser passively Q-switched with a Cr 4+ :YAG crystal upon relative orientations of the switch and an intracavity polariser. The device is shown to operate as an all-optical transistor. One of the main parameters (polarisation) of the Neodymium Laser can be controlled by the relatively weak signal delivered from a CW Laser or Laser diode, the wavelength of which falls into the Cr 4+ :YAG resonant absorption band. The parameters ranges for both the powerful Neodymium and weak controlling Lasers are found, for which the most reliable and effective operation of the device is expected.
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Polarisation of a Neodymium Laser with a passive switch based on a Cr4+ : YAG crystal
Quantum Electronics, 1998Co-Authors: Nikolai N Il'ichev, Alexander V. Kir'yanov, E S Gulyamova, Pavel P PashininAbstract:An experimental investigation is reported of the state of polarisation of the radiation generated in a Neodymium Laser with a passive switch based on a Cr4+ : YAG crystal. A description is provided of the observed dependences. This description is based on the assumption that at each moment of the evolution of lasing the state of polarisation of the Laser radiation represents an eigenstate corresponding to the lowest radiation losses. This state is governed by the relative orientations of the switch and of an intracavity partial polariser, as well as by the radiation energy density in the switch. The calculated results are shown to fit the experimental data.
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Passive Q switching of a Neodymium Laser by a Cr4+ : YAG crystal switch
Quantum Electronics, 1997Co-Authors: Nikolai N Il'ichev, E S Gulyamova, Pavel P PashininAbstract:Theoretical and experimental investigations were made of passive Q switching of a Neodymium Laser by a Cr4+ : YAG switch. Analytic expressions were derived for estimating the output energy of the TEM00 mode of a passively Q-switched Laser from the known parameters of the Cr4+ : YAG switch, of the active element, and of the cavity. The adopted description makes it possible to cover the range from generation of the first spike of a free-running transient to generation of a giant pulse. An experimental study was made of the dependence of the output energy on the cavity parameters, on the material of the active element (in this investigation it was Nd :YAG and Cr, Nd : GSGG), and on the angle of rotation of the Cr4+ : YAG switch. The experimental results obtained agreed to within 30% with calculations.
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Influence of the nonlinear anisotropy of absorption in a passive Cr4+ : YAG switch on the energy and polarisation characteristics of a Neodymium Laser
Quantum Electronics, 1997Co-Authors: Nikolai N Il'ichev, Alexander V. Kir'yanov, E S Gulyamova, Pavel P PashininAbstract:An experimental investigation was made of the polarisation characteristics of a solid-state Neodymium Laser with a passive Cr4+ : YAG switch. The energy and the state of polarisation of Laser radiation were affected radically by the orientation and position of the Cr4+ : YAG switch in the cavity, and also by the nature of an intracavity polariser. The polarisation characteristics of the Laser radiation were determined by a self-induced nonlinear-absorption anisotropy and a self-induced change in the state of polarisation of the Laser radiation during growth of a giant pulse when saturation of the absorption was 'switched on' in the Cr4+ : YAG crystal.
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An Influence of Passive Shutter Cr4+:YAG Latent Anisotropy on Output Energy and Polarisation Characteristics of Neodymium Laser at Passive Q-Switching
Advanced Solid State Lasers, 1997Co-Authors: Nikolai N Il'ichev, Alexander V. Kir'yanov, E S Gulyamova, Pavel P PashininAbstract:Nonlinear absorption anisotropy at the saturation stage in Cr4+ phototropic centers is shown to determine the angular dependencies of output energy and polarisation state of Neodymium Laser Q-switched with Cr4+:YAG crystal.
Сташкевич, И. В. - One of the best experts on this subject based on the ideXlab platform.
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The matrix effect on generation of quasi-three-level continuous wave Neodymium Laser under inhomogeneous pumping / V. I. Gerаsimenko, I. V. Stаshkevitch
Минск : БГУ, 2018Co-Authors: Герасименко, В. И., Сташкевич, И. В.Abstract:Анализируются генерационные характеристики неодимового лазера с квазитрехуровневой схемой для наиболее распространенных кристаллических матриц. Теоретическое исследование энергетических характеристик излучения такого лазера с различными матрицами проведено для стационарного режима генерации. Анализ выполнялся для модели лазера как с продольной накачкой лазерным диодом, так и с поперечной с учетом пространственной неоднородности пучка накачки. Результаты расчетов показывают, что учет пространственной неоднородности пучка накачки при продольном и поперечном возбуждении приводит к росту расчетного значения пороговой мощности накачки и снижению параметра эффективности генерации по сравнению с результатами для точечной модели лазера. Показано, что оптимальными значениями пороговой мощности накачки и параметра эффективности генерации обладают матрицы YAG и GGG по причине более низких значений реабсорбционных потерь.The main generation characteristics of a Neodymium-doped Laser with a quasi-three-level scheme are analyzed for most common crystalline matrices. The energy characteristics of radiation from such a Laser with different matrices in the stationary mode are studied theoretically. The operation of both the end-pumped and transversely-pumped Laser has been simulated. The results of the calculations show that allowance for the spatial inhomogeneity of the pump beam, both for longitudinal and transverse excitation, leads to the increased calculated value of the pump threshold power and to the decreased generation efficiency parameter compared to the results for the point model of Laser. It is demonstrated that the two matrices YAG and GGG have optimal threshold pump powers and slope efficiencies due to lower reabsorption losses
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The matrix effect on generation of quasi-three-level continuous wave Neodymium Laser under inhomogeneous pumping
Минск БГУ, 2018Co-Authors: Герасименко, И. В., Сташкевич, И. В.Abstract:Анализируются генерационные характеристики неодимового лазера с квазитрехуровневой схемой для наиболее распространенных кристаллических матриц. Теоретическое исследование энергетических характеристик излучения такого лазера с различными матрицами проведено для стационарного режима генерации. Анализ выполнялся для модели лазера как с продольной накачкой лазерным диодом, так и с поперечной с учетом пространственной не однородности пучка накачки. Результаты расчетов оказывают, что учет пространственной неоднородности пучка накачки при продольном и поперечном возбуждении приводит к росту расчетного значения пороговой мощности накачки и снижению параметра эффективности генерации по сравнению с результатами для точечной модели лазера. Показано, что оптимальными значениями пороговой мощности накачки и параметра эффективности генерации обладают матрицы YAG и GGG по причине более низких значений реабсорбционных потерь.The main generation characteristics of a Neodymium-doped Laser with a quasi-three-level scheme are analyzed for most common crystalline matrices. The energy characteristics of radiation from such a Laser with different matrices in the stationary mode are studied theoretically. The operation of both the end-pumped and transversely-pumped Laser has been simulated. The results of the calculations show that allowance for the spatial inhomogeneity of the pump beam, both for longitudinal and transverse excitation, leads to the increased calculated value of the pump threshold power and to the decreased generation efficiency parameter compared to the results for the point model of Laser. It is demonstrated that the two matrices YAG and GGG have optimal threshold pump powers and slope efficiencies due to lower reabsorption losses
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The matrix effect on the quasi-three-level Neodymium Laser parameters in the stationary regime / I. V. Stashkevich, V. I. Herasimenka
Минск : БГУ, 2017Co-Authors: Сташкевич, И. В., Герасименко, В. И.Abstract:Проанализированы генерационные характеристики неодимового лазера с квазитрехуровневой схемой для наиболее распространенных кристаллических матриц. Матрица, в которой находятся ионы неодима, определяет основные параметры активной среды – величину штарковского расщепления уровней, время жизни возбужденного состояния, концентрацию ионов неодима, сечений поглощения и излучения. Теоретическое исследование энергетических характеристик излучения такого лазера с различными матрицами проведено для стационарного режима генерации. Анализ выполнялся для модели лазера с продольной диодной накачкой. Показано, что максимальный КПД имеет неодимовый лазер с матрицей калий-гадолиниевого вольфрамата (KGW), следующие по эффективности матрицы – ванадат гадолиния и ванадат иттрия. Наиболее низкую эффективность демонстрируют матрицы из оксида иттрия, иттриево-алюминиевого перовскита (YAP) и гадолиниево-галлиевого граната (GGG). Самый низкий порог генерации имеют лазеры с матрицами иттриево-алюминиевого граната (YAG) и ванадата гадолиния (GVO). = The analysis of the output characteristics of a Neodymium Laser with a quasi-three-level scheme for most common crystalline matrices is presented. The matrix containing Neodymium ions governs the basic parameters of an active medium: the value of Stark level splitting, lifetime of the excited state, maximal concentration of Neodymium ions, absorption and emission cross-sections. The energy characteristics of radiation from such a Laser with different matrices in the stationary mode of generation have been studied theoretically. The modeling has been performed for an end-pumped Laser. It has been shown that the efficiency is at maximum for a Neodymium Laser with potassium-gaddinium tungstate (KGW) matrix, it is lowering for gadolinium and yttrium vanadates, being minimal for the matrices of yttrium oxide, yttrium aluminium perovskit (YAP), and gadolinium gallium garnet (GGG). The lowest lasing threshold is characteristic for Lasers with yttrium aluminium garnet (YAG) and gadolinium vanadate (GVO) matrices
Yu S Tolstyakov - One of the best experts on this subject based on the ideXlab platform.
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measurement of neutral density profile in a tokamak plasma using the principle of Laser induced ionization
Nuclear Fusion, 1995Co-Authors: V I Gladushchak, V K Gusev, Yu M Kantor, Yu V Petrov, G T Razdobarin, V V Semenov, Yu S TolstyakovAbstract:An application is discussed of a new method based on Laser induced ionization that is an alternative to the Laser induced fluorescence diagnostics. Here ionization of the hydrogen upper atomic states gives the local hydrogen densities in a plasma. On the basis of a rate equation analysis for a diffusion dominated plasma a probe saturation flux density of a few MW/cm2 was introduced and appropriate values were used for the plasma diagnostics. A multipulse Neodymium Laser was designed for plasma probing on the FT-I tokamak to measure the neutral density profiles along the plasma diameter. Local neutral densities as low as 1*108 cm-3, which is close to the sensitivity limit of the employed device, have been detected in a single tokamak discharge. The experimental results obtained on the FT-1 tokamak are presented and discussed
A V Kalenskii - One of the best experts on this subject based on the ideXlab platform.
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explosive decomposition of pentaerythritol tetranitrate pellets containing nickel nanoparticles with various radii
Russian Journal of Physical Chemistry B, 2016Co-Authors: N R Nurmukhametov, A A Zvekov, R P Kolmykov, A P Nikitin, M V Ananeva, A V KalenskiiAbstract:The kinetics of the explosive decomposition of pressed pentaerythritol tetranitrate pellets containing nickel nanoparticles with various radii has been investigated experimentally, with the explosion initiated by a Neodymium Laser pulse (wavelength, 1064 nm; pulse duration at half-height, 14 ns), and probability curves for this process have been recorded. The experimental values of critical initiation energy density corresponding to 50% explosion probability are 0.9, 0.7, and 1.4 J/cm2 at a nickel particle radius of 67, 78, and 138 nm, respectively. The initial time interval in which the intensity of light emission accompanying the explosive decomposition increases begins during the action of the pulse and is described by a Gaussian function with an effective constant of k = (1.4 ± 0.1) × 108 s–1, which is independent of the nanoparticle radius. Experimental data of this study can be interpreted within the micro-hotspot model of thermal explosion.
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characteristics of the initiation of the explosive decomposition of petn by the second harmonic pulsed radiation of a Neodymium Laser
Russian Journal of Physical Chemistry B, 2015Co-Authors: B P Aduev, Yu I Liskov, A V Kalenskii, M V Ananeva, D R Nurmukhametov, A A ZvekovAbstract:The critical fluence of the initiation of the explosive decomposition of pentaerythritol tetranitrate (PETN) by the second harmonic of a Neodymium Laser (532 nm) is found to be 12.3 J/cm2. It is shown that, under these conditions, the nonlinear two-photon absorption of light takes place. The critical fluence of the initiation of PETN explosive decomposition in the two-photon absorption mode is calculated within the framework of the thermal explosion model (14.7 J/cm2), which indicates that the thermal mechanism of explosive decomposition is operative under these conditions.
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temperature dependence of the threshold of initiation of pentaerythritol tetranitrate aluminum composite by second harmonic radiation of a Neodymium Laser
Russian Journal of Physical Chemistry B, 2015Co-Authors: Yu I Liskov, A A Zvekov, A V KalenskiiAbstract:The temperature dependence of the threshold of initiation of composite pentaerythritol tetranitrate–aluminum by second-harmonic radiation of a Neodymium Laser (532 nm, 14 ns) is studied. It is shown that the mechanism of initiation of chemical reaction in a PETN–aluminum composite material at temperatures of 300–445 K by first- and second-harmonic Laser radiation is the same, with the differences in the initiation thresholds being associated with a higher efficiency of absorption of second-harmonic radiation by aluminum particles.
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influence of Laser wavelength on the critical energy density for initiation of energetic materials
Combustion Explosion and Shock Waves, 2014Co-Authors: A V Kalenskii, A A Zvekov, M V Ananeva, Yu I Zykov, V G Kriger, B P AduevAbstract:Critical densities of the energy of Laser initiation of PETN containing nanoscale aluminum inclusions at radiation wavelengths of 1064 and 532 nm were measured experimentally. The critical initiation-energy density that corresponds to a 50%th probability of explosion was 1.15 J/cm2 for the first harmonic of a Neodymium Laser and 0.7 J/cm2 for the second. The dependence of the efficiency of radiation absorption by aluminum on the size of metal nanoparticles for the first and second harmonics of a Neodymium Laser is calculated. It is shown that the particle diameter corresponding to the absorption efficiency maximum and the amplitude of the maximum depend on the radiation wavelength. The absorption efficiency maximum for the first harmonic is observed in an inclusion 204 nm in diameter, and for the second, in an inclusion 96 nm in diameter. The amplitude of the maximum increases from 0.351 at a wavelength of 1064 nm to 0.490 at a wavelength of 532 nm. Dependences of the critical initiation energy density for energetic materials on the radius of metallic nanoparticles are calculated. Qualitative agreement between theoretical and experimental results is shown.
