В статье приведены результаты исследований фотостимулированных процессов кристаллизации в стеклах и стеклокристаллических материалах системы MgO-Al2O3-TiO2-SiO2, модифицированных диффузией серебра ионообменной обработкой в солевом расплаве AgNO3/KNO3 при различных температурах, УФ-облучением и дополнительной одноступенчатой термической обработкой. Полученные материалы были исследованы методами оптической и люминесцентной спектроскопии, рефрактометрии, рентгенофазового анализа и измерениями микротвердости. Облучение стекол, подвергнутых ионообменной обработке, приводит к образованию и росту молекулярных кластеров и наночастиц серебра, которые играют роль центров кристаллизации и ускоряют кристаллизацию стекла в процессе его дополнительной термообработки. Экспериментально установлено влияние УФ облучения на показатель преломления и микротвердость прозрачных и опалесцирующих стекол и стеклокристаллических материалов, полученных при дополнительной термообработке стекол, подвергнутых ионному обмену. Հոդվածում ներկայացված են MgO-Al2O3-TiO2-SiO2 համակարգի՝ արծաթի դիֆուզիայի միջոցով մոդիֆիկացված, ապակիների և ապակեբյուրեղային նյու-թերի ֆոտոստիմուլացված բյուրեղացման պրոցեսների ուսումնասիրության արդյունքները: Ապակիները մոդիֆիկացվել են իոնափոխանակային մշակմամբ AgNO3/KNO3 աղերի հալույթում տարբեր ջերմաստիճաններում, ՈՒՄ ճառա-գայթմամբ և լրացուցիչ մեկաստիճանային ջերմային մշակմամբ: Ստացված նյութերն ուսումնասիրվել են օպտիկական և լյումինեսցենտային սպեկտրասկոպիայի, ռեֆրակտոմետրիայի, ռենտգենաֆազային վերլուծության եղանակներով և միկրոկարծրության չափումներով: Իոնափոխանակման ենթարկված ապակիների ճառագայթումը հանգեցնում է մոլեկուլային կլաստերների և արծաթի նանոմասնիկների ձևավորման ու աճի, որոնք հանդես են գալիս որպես բյուրեղացման կենտրոններ և արագացնում են ապակու բյուրեղացումը նրա լրացուցիչ ջերմային մշակման ժամանակ։ Փորձնականորեն հաստատվել է ՈՒՄ ճառագայթման ազդեցությունը թափանցիկ և օպալեսցենտային ապակիների և ապակեբյուրեղային նյութերի բեկման ցուցիչի և միկրոկարծրության վրա, որոնք ստացվել են իոնափոխանակության ենթարկված ապակիների լրացուցիչ ջերմային մշակմամբ: The article presents the results of studies of photostimulated crystallization processes in glasses and glass-crystalline materials of the MgO-Al2O3-TiO2-SiO2 system modified by silver diffusion. The glass was modified by ion-exchange processsing in AgNO3/KNO3 salt melt at different temperatures, UV irradiation and an additional one-step thermal treatment. Received materials were studied using optical and luminescent spectroscopy, refractometry, X-ray phase analysis and microhardness measurements. Irradiation of glasses subjected to ion-exchange treatment leads to the formation and growth of molecular clusters and silver nanoparticles, which play the role of crystallization centers and accelerate the crystallization of glass during its additional heat treatment. The effect of UV irradiation on the refractive index and microhardness of transparent and opalescent glasses and glass-crystalline materials obtained by additional heat treatment of glasses subjected to ion exchange has been experimentally established.

Composite sol-gel materials of the MgO–Al 2 O 3 –ZrO 2 –SiO 2 system were synthesized and the processes of their thermal evolution and crystallization were studied. Application of sol-gel compositions of the MgO–Al 2 O 3 –ZrO 2 –SiO 2 system to the surface of quartz ceramics leads to a significant increase in the mechanical strength of the material. The processes of thermal evolution of the sol-gel composition were studied using IR spectroscopy, X-ray diffraction, electron microscopy, and energy dispersive analysis. It was shown that the formation of the oxide composite structure of materials begins at the stage of wet gels. Treatment of quartz ceramics with composite sols followed by drying and heat treatment up to 1200°C results in modification of the surface layers of the material, which makes it possible to increase the mechanical strength of the material by more than 20%. Sol-gel modifying compositions, upon drying and subsequent heat treatment, form polycrystalline structures bonded to quartz ceramic particles and consisting of various oxide crystals.

In the work, the MgO–Al 2 O 3 –ZrO 2 –SiO 2 coatings on the surface of quartz ceramics were prepared by sol-gel method. The synthesized materials were examined by X-ray phase and electron microscopic analyses. It is shown that composite gels retain an amorphous structure after thermal treatment at 600°C, and the formation and subsequent transformation of various oxide crystal phases is observed after calcination at temperatures above 900°C. The behavior of the thermal evolution of the structure of the obtained gels is generally similar to the course of structural changes occurring during glasses crystallization.

This paper describes the low-temperature polymer-salt synthesis of ZnO–Ag nanopowders and presents the results of studying their structure, morphology, and properties. The methods of X-ray phase analysis and electron microscopy are used to study the structure and morphology of materials. It is found that the resulting nanopowders consist of nanoparticles of about 30 nm. The experiments show that the resulting nanopowders have antibacterial activity against both gram-positive and gram-negative bacteria.

The problems of manufacturing nanoscale Gd2O3:Nd3+ phosphors using the liquid polymer-salt method have been considered. Within the framework of this method, the dual role of polyvinylpyrrolidone (PVP) as an organic solvent in the synthesis process has been determined. On the one hand, it stabilizes the formation of Gd2O3 crystals, preventing their uncontrolled growth and agglomeration, and on the other, it serves as a fuel during decomposition (combustion), contributing to an increase in the reaction temperature and thereby influencing the structural and emission properties of phosphors. It has been shown that successive drying of the initial homogeneous solution containing gadolinium and neodymium salts, as well as PVP, at room temperature for 24 h and heat treatment at 1000°C for 2 h make it possible to obtain high-luminescent near-infrared phosphors Gd2O3:Nd3+, whose crystals are characterized mainly by a cubic structure and an average size of about 40 nm. It has been experimentally confirmed that the developed method is suitable for modifying hollow-core antiresonant optical fibers made of silica glass with thin-film coatings based on the synthesized material and does not cause structural and phase transformation of the formed Gd2O3 crystals. It has been found out that the emission spectra of the nanoscale Gd2O3:Nd3+ phosphors obtained by the polymer-salt method at temperatures of 550 and 1000°C are identical, namely: (1) the shape of the luminescence peaks is the same for both specified heat treatment regimes regardless of intensity, (2) the main lum-inescence peak is located near 1064 nm wavelength and corresponds to the electron transition 4F3/2–4I11/2, and (3) additional luminescence peaks are located near 900 and 1340 nm wavelengths and correspond to the 4F3/2–4I9/2 and 4F3/2–4I13/2 electron transitions, respectively.

The effect of γ-irradiation on optical losses at a wavelength of 1.31 to 1.55 μm in multimode quartz fibers with a core doped with 20 mol % GeO2 is considered. Germanium oxygen-deficient centers in the core material are the main reason for the low radiation resistance of such optical fibers. The elimination of these defects in the MCVD preform technology reduces the radiation-induced attenuation in germanosilicate light guides to a level close to that of light guides with a pure quartz glass core. The increase in optical losses induced by radiation in the studied fibers is largely due to the contribution of Rayleigh scattering.

Photoactive ZnO–SnO 2 –Ag(AgCl) nanomaterials capable of generating chemically active single oxygen under action of UV and blue light are synthesized using a polymer–salt method. The structure and properties of these materials are studied by optical and luminescence spectroscopy, as well as by X-ray diffraction and electron microscopy analyses. It is found that the structure of the ZnO–SnO 2 –Ag(AgCl) materials consists of hexagonal ZnO crystals with a wurtzite structure, tetragonal SnO 2 nanocrystals with a rutile structure, and Ag and AgCl crystals. The materials consist mainly of nanoparticles 50–60 nm is size. They are characterized by the ability to generate chemically active singlet oxygen and have antibacterial properties against both Gram-positive and Gram-negative bacteria. An increase in the concentration of silver in the materials enhances their antibacterial properties.

Photoactive ZnO-SnO2-Ag(AgCl) nanomaterials have been prepared by polymer-salt method. Prepared materials able to generate singlet oxygen under UV and blue light irradiation. Materials structure and properties have been studied by optical and luminescence spectroscopy, XRD and SEM analysis. It was found that the structure of ZnO-SnO2-Ag(AgCl) materials consists of hexagonal ZnO, tetragonal SnO2, Ag and AgCl crystals having size 50÷60 nm. Obtained materials able to generate chemically active singlet oxygen under UV irradiation and have high bactericidal properties against both gram-positive and gram-negative bacteria. The increase of Ag content enhances the bactericidal properties of prepared materials.

The article considers the aspects of nanoscale Gd2O3:Nd3+ phosphors synthesis using the liquid polymer-salt method. Within the framework of the method, the double role of polyvinylpyrrolidone (PVP) as an organic solvent in the process of synthesis was determined. On the one hand, PVP stabilizes the process of Gd2O3 crystals formation, preventing their uncontrolled growth and aggregation. On the other hand, PVP serves as a fuel during decomposition (combustion) increasing the temperature of reaction and thus influencing the structural and emission properties of phosphors. It is shown that drying of the initial homogeneous solution containing gadolinium and neodymium salts and PVP at the room temperature for 24 hours followed by thermal treatment at the temperature of 1000 °C for 2 hours allow formation of highly luminescent Gd2O3:Nd3+ near-infrared phosphors. The crystals grown are characterized mainly by the cubic structure and an average size of 40 nm. Experimental results confirmed that the developed method is appropriate for modification of a structure of silica hollow-core antiresonant fibers with thin-film coatings based on the synthesized material and does not result in structural and phase conversion of Gd2O3 crystals. It is found out that emission spectra of nanoscale Gd2O3:Nd3+ phosphors formed by the polymer-salt method at the temperatures of 550 °C and 1000 °C are identical, as follows: 1) the shape of the luminescence peaks is the same for the two mentioned regimes of thermal treatment regardless of intensity, 2) the main luminescence peak is located near the wavelength of 1064 nm and corresponds to a 4F3/2-4I11/2 electron transition, 3) additional luminescence peaks are located close to 900 nm and 1340 nm and refer to 4F3/2-4I9/2 and 4F3/2-4I13/2 electron transitions respectively.

This work presents results of researhes of fabricated pilot sample of chiral few-mode optical fiber (FMF) with induced twisting of 10 and 66 revolutions per meter, core diameter 11 µm (that almost corresponds to standard singlemode optical fibers), typical “telecommuniction” cladding diameter 125 µm and improved height of step refractive index profile. Proposed few-mode optical fiber supports 4 guided modes over “C”-band. We considered design and selection of desired technological parameters, based on results of computations, performed by both rigorous and approximation methods. Spectral curves of dispersion parameters are reprented as well as results of experimental measurements near-field laser beam profile and spectral and pulse responces of laser-excited optical signals.

Новый класс многомодовых оптических волокон с диаметром сердцевины 100 мкм для компактных мультигигабитных сетей передачи данных разного назначения А.В.Бурдин 1,2,3,* , В.А.Бурдин 2 , К.В.Дукельский 1 , О.Е.Наний 4 , Т.О.Базаров 4 , В.В.Демидов 1 , А

The causes of the occurrence and the method of the elimination of defects of non-bridging oxygen in multimode fluorosilicate optical fibers prepared by the modified method of chemical vapor deposition are considered. The solution is the use of support tubes obtained by quartz surfacing in a hydrogen atmosphere. In this case, there is no absorption band in a range of 630 nm caused by nonbridging oxygen in the spectrum of optical losses of gradient fluorosilicate optical fibers of W-type. Attenuation in a visible spectrum range is mainly determined by the level of Rayleigh scattering and the mode dispersions at a wavelength of 342 and 683 nm are 1.2 ± 0.1 and 0.7 ± 0.2 ps/m, respectively.

We describe a dual-band machine vision system for controlling the shape of a large space-based antenna and propose a technique for multiplexing the video signals from the visible and infrared sensors. We list the specifications for the basic components of the dual-band video system-the video cameras and the objectives. An analysis is performed to determine the advantages of the proposed system over traditional engineering design solutions. (C) 2018 Optical Society of America.

© К.В. Дукельский , Г.М. Ермолаева , М.А. Ероньян , А.В. Комаров , А.А. Реуцкий , В.Б. Шилов , А.А. Щеглов 3 1 Санкт-Петербургский государственный университет телекоммуникаций им. проф. М.А. Бонч-Бруевича, 193232 Санкт-Петербург, Россия 2 Государственный оптический институт им. С.И. Вавилова, 199034 Санкт-Петербург, Россия 3 Концерн ” Центральный научно-исследовательский институт ” Электроприбор“, 197046 Санкт-Петербург, Россия 4 НПО Научно-исследовательский и технологический институт оптического материаловедения Государственного оптического института им. С.И. Вавилова, 192171 Санкт-Петербург, Россия 5 Университет ИТМО, 197101 Санкт-Петербург, Россия