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1
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Induced Absorption in Gadolinium Gallium Garnet Irradiated by High Energy ^{235}U Ions

100%
Potera P., Ubizskii S., Sugak D., Schwartz K.
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EN
The present work is devoted to investigation of optical absorption in pure Gd_{3}Ga_{5}O_{12} (GGG) single crystals in the spectral range 0.2-1.1 μm induced under influence of the ^{235}U ions irradiation with energy 2640 MeV and a fluence 10^{9}-10^{11} cm^{-2}. The induced absorption for 10^{9} cm^{-2} is caused by recharging of point defects, both growth ones and impurities. After irradiation by ^{235}U ions with fluences starting from 3 × 10^{9} cm^{-2} the absorption rise is probably caused by contribution of the lattice destroying as a result of heavy ion bombardment as well as radiation displacement defects.
2
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Optical in situ Study of Reduction/Oxidation Processes in Cr,Mg:YAG Epitaxial Film

100%
Buryy O., Ubizskii S., Syvorotka I., Becker K.
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EN
The changes of the optical absorption spectra of Cr,Mg:YAG epitaxial film caused by high-temperature redox treatment are investigated by means of in situ spectroscopy. The spectra were registered in the visible and near-IR spectral regions at temperatures up to 1100 K. The kinetics of optical absorption changing were obtained in the temperature range from 936 K to 1091 K and were described by mathematical model connecting the chromium recharging process with oxygen vacancies diffusion. The parameters of the model were determined from the approximations of the experimental kinetics.
3
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Optical Properties of GGG Epitaxial Films Grown from PbO-B₂O₃-V₂O₅ Flux

88%
Syvorotka I., Sugak D., Luchechko A., Zhydachevskyy Y., Ubizskii S.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
954-958
EN
The paper reports a growth of the high-quality Gd₃Ga₅O₁₂ (GGG) homoepitaxial films by the liquid phase epitaxy technique using the PbO-B₂O₃ and PbO-B₂O₃-V₂O₅ fluxes. The influence of the flux composition containing V₂O₅ as well as the growth temperature is discussed basing on the optical absorption and the electron probe micro analysis results.
4
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The Passively Q-switched Microchip Nd:YAG Laser Optimization for Rangefinder Applications

76%
Buryy O., Iznin A., Syvorotka I., Sugak D., Ubizskii S., Vakiv M.
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issue 1
238-243
EN
The problem of Q-switched microchip Nd^{3+}:YAG/Cr^{4+}:YAG laser optimization is considered. In accordance with requirements of laser location, the optimization consists in determination of such values of the saturable absorber (Cr^{4+}:YAG) thickness, the output laser mirror reflectivity and the pumping power, that ensure the generation of the sufficiently short ( ≈0.5 ns) laser pulses at the repetition rate of about 10 kHz and the peak power of about 1 kW or higher. Firstly, the dependences of the laser radiation parameters on the constructive ones are analyzed in the frames of Xiao-Bass model of Q-switched microchip laser. The obtained dependences are used for laser optimization. As it is shown, the parameters of laser radiation close to predominating ones are achieved at the absorber thickness of 140 μm, the output mirror reflectivity of 0.97 and the pumping power of 2.5 W.
5
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Eight-Channel Optical Add Drop Multiplexer Based on Ring Resonator Using LNOI Channel Waveguides

76%
Kumar H., Janyani V., Buryy O., Ubizskii S., Sugak D., Singh G.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
997-999
EN
In this paper we report on an eight-channel optical add drop multiplexer based on ring resonator using lithium niobate on insulator channel waveguides. It is suitable for a DWDM-GPON network with channel spacing of 100 GHz in C-band and data rate is 10 Gbps. The insertion loss at the drop port is maximum 1.2 dB and the Q-factor is 1636. It can be used as multiplexer as well as demultiplexer in 8-channel DWDM systems.
6
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Effect of Lutetium Co-Doping on the Main Dosimetric Peak of YAP:Mn²⁺ Thermoluminescent Detectors

76%
Zhydachevskyy Y., Glowacki M., Martynyuk N., Ubizskii S., Berkowski M., Suchocki A.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
973-976
EN
An effect of lutetium co-doping on photoluminescent and thermoluminescent properties of the Mn²⁺-doped (Lu-Y)AP crystals (with Lu content from 0 to 20% with respect to Y) grown by the Czochralski technique has been studied. It was found that the maximum of the thermoluminescent peak at 200°C is shifted towards higher temperatures at Lu content more than 5%. At the same time the position of the second thermoluminescent peak near 350°C remains unchanged. The observed changes in the thermoluminescent peak position are discussed in terms of the point defects of the material.
7
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Thermal Behaviour of PrCo_{1-x}Fe_xO₃ Probed by X-ray Synchrotron Powder Diffraction and Impedance Spectroscopy Measurements

76%
Pekinchak O., Sugak D., Ubizskii S., Suhak Y., Fritze H., Vasylechko L.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
798-801
EN
Crystal structure and transport properties of the mixed praseodymium cobaltites-ferrites PrCo_{1-x}Fe_xO₃ have been studied in the temperature range of 298-1173 K by a combination of in situ X-ray synchrotron powder diffraction and temperature dependent impedance spectroscopy measurements. In situ high temperature powder diffraction examination of PrCo_{1-x}Fe_xO₃ series revealed considerable anomalies in the lattice expansion which are especially pronounced for the cobalt-rich specimens. These anomalies, which are reflected in a sigmoidal dependence of the unit cell dimensions and in the considerable increase of the thermal expansion coefficients, are obviously associated with transitions of Co^{3+} ions from low spin to the higher spin states and the coupled metal-insulator transitions, occurring in in rare earth cobaltites at the elevated temperatures. Indeed, the temperature-dependent impedance measurements clearly prove the change of conductivity type from dielectric to the metallic behaviour in the mixed cobaltite-ferrites PrCo_{1-x}Fe_xO₃ at the elevated temperatures.
8
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In situ Investigation of OH^{-} Absorption in LiNbO_{3} and LiNbO_{3}:MgO Crystals during Reducing/Oxidizing Annealing

76%
Sugak Y., Sugak D., Zhydachevskii Y., Solskii I., Buryy O., Ubizskii S., Becker K.
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EN
The work presents experimental results of an in situ investigation of the OH^{-} absorption in pure and MgO-doped LiNbO_{3} crystals during reducing (95% Ar + 5% H_{2}) and oxidizing (O_{2}) high-temperature treatments in the temperature range from room temperature to 820 K. The absorption spectra measured in situ at high temperatures in reducing/oxidizing atmospheres have been analyzed. The origin of the changes in optical absorption caused by heating of the crystal is discussed in terms of the OH-bonds orientation change.
9
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Photoluminescence and Thermoluminescence of the Oxygen-Deficient YAG, YAP, and YAM Phosphors

64%
Zhydachevskyy Y., Kamińska I., Glowacki M., Kilian A., Ubizskii S., Bilski P., Berkowski M., Fronc K., Elbaum D., Suchocki A.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
977-980
EN
Photoluminescence and thermoluminescence of the oxygen-deficient Y₃Al₅O₁₂ (YAG), YAlO₃ (YAP) and Y₄Al₂O₉ (YAM) ceramics has been studied. Corresponding ceramic samples prepared by the same way however in oxidizing conditions (in air) were studied for comparison. The observed luminescent properties of the materials are related to the F-type centers created on the basis of oxygen vacancies, antisite (Y_{Al}) defects and uncontrolled Tb³⁺ impurity ions.
10
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Investigation of Co Ions Diffusion in Gd₃Ga₅O₁₂ Single Crystals

52%
Sugak D., Syvorotka I., Yakhnevych U., Buryy O., Vakiv M., Ubizskii S., Włodarczyk D., Zhydachevskyy Y., Pieniążek A., Jakiela R., Suchocki A.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
959-964
EN
Spatial changes of properties of Gd₃Ga₅O₁₂ (GGG) single crystals caused by diffusion of cobalt ions during high-temperature annealing (1200°C, 24 h) in Co₃O₄ powder are investigated. The registration of these changes was carried out by optical spectrophotometry, microscopy and micro-Raman scattering methods. Changes in structure of near-surface layers of the crystal were investigated by X-ray diffraction technique. It was shown that the additional absorption induced by annealing is related to intra-center optical transitions in Co²⁺ ions, which occupy tetrahedral positions in the garnet structure at the distances of 250-500 μm from the crystal surface. The dependence of induced absorption with depth has got a non-monotonous character with a maximum at 400 μm. A comparison of the results obtained by different methods allows to suppose that the thermal treatment of GGG in the presence of cobalt ions leads to formation of the structurally and chemically non-uniform layer with a width about 500 μm.
11
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Optical Investigation of the Cu Ions Diffusion into Bulk Lithium Niobate

52%
Sugak D., Syvorotka I., Yakhnevych U., Buryy O., Martynyuk N., Ubizskii S., Zhydachevskyy Y., Suchocki A., Kumar H., Janyani V., Singh G.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
965-972
EN
Spatial changes of optical properties of bulk LiNbO₃ crystal were investigated after annealing in CuO powder. The incorporation of copper ions into the crystal was confirmed by registration of additional absorption spectra that revealed formation of the absorption bands of both Cu⁺ (400 nm) and Cu²⁺ (1000 nm) ions. The changes of optical absorption caused by thermal treatment were registered along the direction of diffusion by the probe beam perpendicular to this direction. The anisotropy of diffusion was revealed. The maxima were observed on the depth dependences of additional absorption both for the wavelengths of 400 and 1000 nm for all main crystallographic directions. The concentrations of copper ions were calculated in accordance with the Smakula-Dexter formula. The X-ray diffraction study revealed reflexes which probably belong to CuNb₂O₆, CuNbO₃ and CuO. The halo was observed on these diffraction patterns that confirms the formation of the scattering centers (about 1 nm in diameter) in the near-surface region.
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