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426 results on '"Ovchinnikov, O."'

14. Exfoliated Bi2Te3 nanoparticle suspensions and films: morphological and nonlinear optical characterization

Author

Ganeev Rashid A., Popov V. S., Zvyagin A. I., Lavrentyev N. A., Mirofyanchenko A. E., Mirofyanchenko E. V., Shuklov I. A., Ovchinnikov O. V., Ponomarenko V. P., and Razumov V. F.

Subjects
bismuth telluride nanoparticles, nonlinear refraction, reverse saturable absorption, saturable absorption, synthesis, Physics, QC1-999
Abstract

Bismuth telluride nanoparticles (NPs) attract attention due to the growth of sensitivity of the Bi2Te3 NPs-containing registrars in the near- and mid-infrared ranges. We describe the synthesis and characterization of these structures and analyze the low-order nonlinear optical properties of the colloidal suspensions and thin films containing Bi2Te3 NPs using 1064 and 532 nm, 10 ns pulses. Colloidal Bi2Te3 NPs demonstrate saturable absorption and positive nonlinear refraction (saturation intensity 7 × 108 W cm−2, nonlinear absorption coefficient β SA = −7 × 10−8 cm W−1, nonlinear refractive index γ = 9 × 10−12 cm2 W−1), while at stronger excitation by 532 nm, 10 ns pulses the reverse saturable absorption dominates over other nonlinear optical processes. We achieved significant growth of the nonlinear optical parameters of the thin films containing these NPs (film thickness l = 60 nm, β SA = −1.2 × 10−4 cm W−1, γ = 5 × 10−7 cm2 W−1 in the case of 532 nm probe radiation and β = −5 × 10−5 cm W−1, γ = 6 × 10−8 cm2 W−1 in the case of 1064 nm probe radiation) compared with colloidal Bi2Te3 NPs and discuss the observed peculiarities of the nonlinear response of Bi2Te3 nanostructures.

Published
2021
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19. PRODUCING ADVANCED ALLOYS BASED ON TITANIUM ALUMINIDES FOR MODERN AIRCRAFT ENGINE MANUFACTURING.

Author

Ovchinnikov, O. V., Akhonin, S. V., Berezos, V. O., Severin, A. Yu., Galenkova, O. B., and Shevchenko, V. G.

Subjects
TITANIUM aluminides, AIRPLANE motors, ARC furnaces, TITANIUM alloys, ELECTRON beam furnaces, INGOTS
Abstract

Works have been performed on optimization of the technological scheme of producing ingots for consumable electrodes with a stable chemical composition and properties. The paper presents the results of studying an ingot of 195 mm diameter from a titanium aluminide-based alloy of Ti-28Al-7Nb-2Mo system, made by double electron beam remelting. Further ingot remelting in the arc furnace was performed, which allowed producing a homogeneous and defect-free ingot of an optimal composition of Ti-28Al-7Nb-2Mo-0.3 (Y, Re, B). The influence of modifying on the structure and properties was studied. It was determined that addition of surfactants promotes refining of the structural components and improvement of the alloy mechanical properties. [ABSTRACT FROM AUTHOR]

Published
2024
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21. $a \to e^+ e^-$ decay in a model with induced coupling to leptons

Author

Mikheev, N. V., Ovchinnikov, O. S., and Vassilevskaya, L. A.

Subjects
High Energy Physics - Phenomenology
Abstract

The process of electron-positron pair production by axion propagating in an external magnetic field is investigated in a model with only induced axion coupling to leptons. Contributions of the lowest and higher Landau levels are analyzed. The results we have obtained demonstrate a strong catalyzing influence of the field., Comment: 7 pages, latex. To be published in Mod. Phys. Lett. A

Published
1998
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23. Field-induced axion decay $a \to e^+ e^-$ in KSVZ-model

Author

Mikheev, N. V., Ovchinnikov, O. S., and Vassilevskaya, L. A.

Subjects
High Energy Physics - Phenomenology
Abstract

The axion decay into electron-positron pair $a \to e^+ e^-$ is studied in an external magnetic field in KSVZ-model where axions have only induced coupling to leptons. The axion lifetime in the field decreases with energy and field strength to seconds., Comment: 4 pages, latex. Talk given at the International Workshop on Particle Physics and the Early Universe ``COSMO'97'', Ambleside, Lake District, England, 15-19 September 1997

Published
1997
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24. Enhancement of Nonlinear Absorption of Nanosecond Laser Pulses in Mixtures of Ag2S Quantum Dots and Silver Nanoparticles.

Author

Zvyagin, A. I., Chevychelova, T. A., Chirkov, K. S., Smirnov, M. S., Ovchinnikov, O. V., Selyukov, A. S., and Latyshev, A. N.

Abstract

The Z-scan method is used to analyze the nonlinear optical response in mixtures of colloidal Ag2S quantum dots with a diameter of 2.5 nm, passivated with thioglycolic acid, and spherical silver nanoparticles with a diameter of 6 nm, passivated with sodium citrate, in the field of 10 ns pulses of the second harmonic (532 nm) of an Nd3+:YAG laser. An enhancement of nonlinear absorption in mixtures of Ag2S quantum dots with silver nanoparticles is established against the background of suppression of nonlinear refraction. Quenching and acceleration of the luminescence kinetics of Ag2S quantum dots in the presence of silver nanoparticles indicates an interaction between the mixture components. The observed patterns in the nonlinear optical response are explained by changes in the probabilities of optical transitions involving local levels of structural defects of Ag2S colloidal quantum dots under the polarizing effect of plasmonic spherical silver nanoparticles. [ABSTRACT FROM AUTHOR]

Published
2023
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46. Luminescence of Ag2S/SiO2 Colloidal Quantum Dots Decorated with Small Au Nanoparticles.

Author

Grevtseva, I. G., Ovchinnikov, O. V., Smirnov, M. S., Kondratenko, T. S., Perepelitsa, A. S., and Hussein, A. M. H.

Subjects
*SEMICONDUCTOR nanocrystals, *QUANTUM dots, *GOLD nanoparticles, *LUMINESCENCE, *LUMINESCENCE measurement
Abstract

A tenfold increase in the quantum yield of defect luminescence in the region of 750 nm with a simultaneous increase in its decay time from 4 to 200 ns, due to decoration of surface of quantum dots (QDs) Ag2S/SiO2 (5.0 ± 1.5 nm) with Au nanoparticles (NPs) (2.0 ± 0.5 nm). Based on analysis of the luminescence kinetics at temperatures of 77 and 300 K, it was concluded that such a nonspecific manifestation of the plasmon–exciton interaction is caused by the influence of polarization effects from Au NPs on the properties of shallow traps involved in the formation of the defect luminescence kinetics of Ag2S/SiO2 QDs. [ABSTRACT FROM AUTHOR]

Published
2022
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47. Nonlinear Optical Properties of Colloidal PbS and Ag2S Quantum Dots Passivated with 2-Mercaptopropionic Acid.

Author

Zvyagin, A. I., Chevychelova, T. A., Chirkov, K. S., Smirnov, M. S., and Ovchinnikov, O. V.

Abstract

A Z-scan study is performed of the nonlinear optical response of hydrophilic colloidal PbS and Ag2S quantum dots with average sizes of 2.2 and 2.9 nm, respectively, passivated with 2-mercaptopropionic acid (2-MPA). A Nd3+:YAG laser is used at wavelengths of 355 and 532 nm and a pulse length of 10 ns. It is found that the PbS/2-MPA and Ag2S/2-MPA colloidal solutions exhibit nonlinear refraction (defocusing) at both wavelengths. The saturation character of the dependence of the coefficient of nonlinear absorption on the intensity of laser radiation is revealed. It is established that localized states (e.g., the center of recombination luminescence) are responsible for both nonlinear optical effects. [ABSTRACT FROM AUTHOR]

Published
2022
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