The review primarily considers the scientific progress in the identification of impurities, molecular compounds, and heterophase inclusions in high-purity sulfur. Methods for their determination, established by the present time, based on atomic emission spectrometry, mass spectrometry, colorimetry, gravimetry, titrimetry, turbidimetry, conductometry, gas chromatography, infrared spectrometry, chromatography–mass spectrometry, and laser ultramicroscopy are thoroughly characterized.

Расширены сведения о молекулярной форме примесей углерода, водорода и кислорода в особо чистом селене. Методом хромато-масс-спектрометрии в селене впервые установлено присутствие и содержание примесей углеводородов, их галогенпроизводных, серо- и селенсодержащих веществ. Методом атомно-эмиссионной спектроскопии с индуктивно-связанной плазмой определено содержание примесей 46 элементов в селене. Данные о молекулярной форме примесей углерода, кислорода и водорода в коммерческом особо чистом селене облегчат выбор и оптимизацию методов его дальнейшей глубокой очистки.

— This paper presents additional data on carbon, hydrogen, and oxygen impurities in molecular form in extrapure selenium. Using gas chromatography/mass spectrometry analysis, selenium has been shown for the first time to contain hydrocarbons, halogenated hydrocarbons, and sulfur- and selenium-containing substances. Forty-six elemental impurities were detected in selenium by inductively coupled plasma atomic emission spectroscopy. Data on carbon-, oxygen-, and hydrogen-containing molecular impurities in commercially available extrapure selenium will be helpful in choosing and optimizing methods for its further ultrapurification.

The analysis of the current state of technology, prospects for the development and application of fiber light guides made of chalcogenide glasses with minimal attenuation at wavelengths from 2 to 15 microns (near and medium IR ranges) is carried out. The literature data on the effect of irradiation of sulfide-arsenic light guides by gamma-quantum, electron, and neutron fluxes on the characteristics of optical fibers are considered. The areas of possible use of chalcogenide light guides in conditions of radiation exposure are analyzed.

Glassy chalcogenides AVBVI obtained by solidification of high-temperature melts inherit the polymolecular nature of the melt. The influence of this circumstance on the optical properties of glasses is important for the fabrication of optical fibers and has not been adequately studied. Bulk samples of high-purity As40 – xS60 + x glasses (0 < x < 5) containing less than (1–2) × 10–5 wt

Glassy chalcogenides AVBVI obtained by solidification of high-temperature melts inherit the polymolecular nature of the melt. The influence of this circumstance on the optical properties of glasses is important in connection with the use of optical fibers for fabrication and has not been adequately studied. Bulk samples of high-pure glasses As40 – xS60 + x (0 x 5) with the content of metal and silicon impurities less than 0.1‒0.2 ppm wt., carbon, oxygen, hydrogen compounds – no more than 0.5–1 ppm wt. and optical fibers from them were obtained. The IR spectra of bulk samples 12 cm long and optical fibers up to 15 m long were recorded in the spectral range 1000–2000 cm–1. Absorption bands with maxima near 1950, 1805, 1460, and 1320 cm–1, due to the content of superstoichiometric sulfur in glass, were found in the spectra of bulk samples and fibers, and the corresponding values of the extinction coefficients were determined. The results of the study allow us to consider the As2S3 stoichiometry as a factor that significantly affects the optical characteristics of glass.

We proposed a new concept of increasing the plasticity of chalcogenide glasses while maintaining a high glass transition temperature. The main idea of this concept lies in the formation of Ag-Ag metallophilic interactions when silver chalcogenide is introduced into the glass composition. This suggestion was confirmed by the experimental study of glasses based on the Ag2Se-Sb2Se3-GeSe2 system. It was observed that the introduction of 40 mole percent of Ag2Se into the glass composition leads to the increase of its plasticity by 3.5 times, whereas the glass transition temperature of such glass remains higher than 200 degrees C. The most typical application area of these materials is infrared (IR) optics. In our case, the addition of silver not only improves the mechanical properties of a glass but also allows one to keep the position of the fundamental absorption edge in the near-IR region (900 nm), which is quite suitable for the aforementioned applications.

Methods for manufacture of high-Q bulk microresonators from As2S3 and GaAs are elaborated. Obtained Q-factor at 1550 nm are shown to be comparable with record values for these materials: 7·106 for GaAs and 8·106 for As2S3.

The actively developed direction at the present time is the production of chalcogenide glasses with a low content of impurities and the manufacture of optical fibers with low optical losses on their basis. The transparency of glasses, characterized in optical fibers by the level of optical losses, refers to the key parameters of optical fibers and determines the attenuation of the signal passing through the fiber. The lowest optical losses that were achieved in multimode fibers from sulfide, selenide, and arsenic sulfoselenide glasses are 12-14; 60 and 67 dB/km, respectively. Real level of optical losses in chalcogenide glass fibers are two or more orders higher than theoretically predicted. The magnitude of this discrepancy contains the constituent parts associated with the nature and properties of glass, with the conditions for the manufacture of glass and optical fibers as well as with the methodology for the theoretical evaluation of the magnitude of intrinsic optical losses in glass. In this paper the structure, the main sources of excessive losses, the ways of approximation of real and theoretically predicted losses are considered on the example of optical fibers produced from arsenic-based chalcogenide glasses.

The IR spectrometric method for determination of hydrogen impurities in the form of SH-groups in liquid sulfur is developed. The temperature dependence of the content of SH-groups in sulfur samples in the range of 300-550 degrees C is studied. The technique for deep sulfur purification including vacuum distillation, passing sulfur vapor through catalysts based on silicon, aluminum and cerium oxides, and filtering the vapor using high-purity silica-glass micro-filters is developed. The sulfur containing 40 +/- 4 ppb(at) SH-group is prepared. By using the high-purity sulfur samples of various origins, Ga5Ge36 S-59 glasses are synthesized. Sulfur is shown to be the essential source of hydrogen impurity and heterogeneous inclusions in the glasses. The minimum hydrogen content in the form of SH-groups in the Ga5Ge36S59 glass sample, prepared from the sulfur purified using the developed technique, is 0.10 +/- 0.02 ppm(at). The content of heterogeneous micron-sized inclusions in this glass sample is not exceed 10 pieces/cm(3).

The heat capacity of four samples of high-purity chalcogenide glasses GeSx:nBi (x = 1.25, 1.35, 1.4, 1.6; n = 1 at. %) in the region of 300-750 K was measured by the differential scanning calorimetry (DSC) method. According to the data obtained, standard thermodynamic functions (STF) were calculated with regard for the established characteristics of the glass transition: heat capacity C-P degrees(T), enthalpy H degrees(T) - H-l degrees(0), entropy S degrees(T) - S-l degrees(0) and Gibbs energy G degrees(T) - H-l degrees(0) in the region T -> 0 to 750 K in the glassy and "supercooled liquid" states. For these glasses, the glass transition temperatures (T-g) ranged from 620 to 655 K increasing with increasing S content. The linear expansion coefficients were measured at room temperature and the average value was (15 +/- 0.225).10(-6) K-1. The use of parametric similarity of properties in the framework of the model statistical approach makes it possible to predict the STF for unexplored glasses of this series. The standard enthalpies of glass formation for each composition were calculated using the valence-state (VSM) model, and the valence-orbital characteristics of Ge, S, and Bi atoms were calculated which made it possible to determine the dependence of the charge distribution on these atoms on the sulfur content of the glass composition.

It has been established that rare earth elements (REE), as alloying additives, are a significant source of hydrogen and oxygen impurity in glasses of Ge - S and Ge - As - S systems. A method has been developed that includes loading germanium in the form of monosulfide and high-temperature annealing of REE and their compounds in sulfur vapor, reducing content of absorbing impurities in sulfide-germanium glasses. Samples of especially pure glasses of Ge42.5S57.5 and Ge35As10S55 composition doped with praseodymium up to 1450 ppm(at) were prepared. The impurity content of hydrogen and oxygen in the form of SH-groups and Ge-O in the best glass samples was 0.02-0.06 ppm(wt) and <0.1-0.2 ppm(wt), respectively. The absorption coefficients and the absorption cross section were determined for various energy states of the Pr3+ ion in Ge35As10S55 glass. The luminescence intensity of Pr3+ ions in the spectral ranges 2.0-2.8 and 3.5-5.8 mu m in Ge42.5S57.5 glasses is by 3 orders of magnitude higher than in Ge(35)As(1)0S(55) glasses. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

The molecular composition of impurities in special purity selenium was studied for the first time using the gas chromatography-mass spectrometry method. The concentrate of impurities with boiling points below that of the selenium was obtained by its vacuum distillation. The impurities were condensed and frozen from the vapor phase beyond the zone of the complete condensation of selenium vapors. The analysis of the obtained samples was performed using an Agilent 6890 / 5973N gas chromatography-mass spectrometer with a quadrupole mass analyzer. The samples' input into the analytical device was carried out using a vacuum system made of stainless steel tubes. For the separation of impurities, GS-GasPro 60 m × 0.32 mm capillary adsorption columns with a silica gel sorbent and a 25 m × 0.26 mm polytrimethylsilylpropine (PTMSP) sorbent were used to separate the substances with low and quite high boiling temperatures. Their combined use made it possible to determine a wider range of impurities in selenium. The impurities were identified by comparing the experimental mass spectra with the data from the NIST database. In the absence of mass spectra of the detected substances in this library, their identification was carried out by restoring the composition with the fragment ions. Thus, the mass spectrum of the COSe impurity, which was not found in the literature, was decoded and described. In selenium, impurities of constant gases, carbon dioxide, C 2 – C 6 hydrocarbons, aromatic hydrocarbons, carbonyl sulphide, some chlorinated hydrocarbons, cyan, selenium compounds, and ethers were identified. Keywords: selenium of special purity, impurities, identification, gas chromatography-mass spectrometry, capillary column (Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.1.007 А .Iu. Sozin, M.F. Churbanov, О .Iu. Chernova, T.G. Sorochkina, G.E. Snopatin, I.V. Skripachev, Iu. А . Lesina G.G. Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences, Tropinina Str.,49, Nizhny Novgorod, 603950, Russian Federation

Lately, there has been a strong incentive for the development of photonics devices which operate farther in the infrared wavelength range. In this communication, we present a study of the photosensitivity to femtosecond pulses of Mid- Infrared transmitting materials, which are promising candidates to be used as substrates for photo-induced devices, namely, Germanium-Sulfide glass (Ge-S), Barium Gallo-Germanate glass (BGG), and sapphire. We report the formation of single mode waveguides operating at a wavelength of 2.85 μm, in all three materials. In addition, the inscription of a low-loss depressed clad waveguide in sapphire is demonstrated.

We demonstrate a broadband As2S3-based fiber coupler operating up to the 5.4 mu m wavelength range developed by using a fused biconical tapering technique. During the manufacturing process, real-time data monitoring of the coupling ratio was at 2.64 mu m. The measurement of minimal excess loss was at less than 1 dB in the range of 5-5.4 mu m. Also, fiber bend loss was numerically analyzed to determine optimal coupler geometric parameters. (C) 2019 Optical Society of America

The article discusses the problem of preparing arsenic-sulfide glasses for fiber optics with a low content of impurity hydrogen which determines the level of optical absorption loss in the range of 2-6 mu m. The sources of impurity hydrogen in the form of SH-groups with its content of 1-100 ppb wt, their relative contribution and the effect on the transparency of bulk samples of glasses and optical fibers are considered. The results of studies of the contaminating effect of the apparatus material and the environment in the preparation of arsenic-sulfide glasses and optical fibers on their basis with low optical losses are presented. (C) 2018 Elsevier B.V. All rights reserved.

We have determined the molecular composition of organic impurities in extrapure sulfur obtained by the distillation purification of sulfur recovered from gaseous hydrocarbons. Using vacuum extraction, we obtained a concentrate of impurities highly volatile compared to the major component. Gas chromatography/ mass spectrometry analysis indicated the presence of impurities in the form of hydrocarbons with up to eight carbon atoms and their thio, oxy, and nitro derivatives. The detection of this group of impurities accounts for the distinctive features of the preparation of sulfur with low carbon and oxygen contents through ultrapurification of gas-derived sulfur.

Впервые с использованием метода хромато-масс-спектрометрии исследован молекулярный примесный состав высокочистой серы. Для пробоподготовки образцов использовали извлечение примесей из серы при ее вакуумной перегонке. Масса пробы серы, из которой проводили извлечение, составляла до 1 кг. Примеси конденсировали в стеклянных ампулах, из которых затем осуществляли их напуск в систему дозирования хромато-масс-спектрометра. Для их разделения использовали капиллярные адсорбционные колонки GS-GasPro с модифицированным сили кагелем в качестве сорбента и с политриметилсилилпропином (ПТМСП). Совместное применение этих колонок позволяет определять в сере широкий круг примесных веществ. Идентификацию примесей проводили сравнением их экспериментальных масс-спектров с данными базы NIST. В случае наложения хроматографических пиков примесей их идентификацию проводили по характеристическим ионам и с использованием вычитания пиков ионов, принадлежащих соседнему компоненту. Установлено, что при использовании колонки с политриметилсилилпропином кислороди азотсодержащие органические вещества элюируются в виде ассиметричных пиков с крутым фронтом и размытым тылом. В высокочистой сере идентифицированы примеси постоянных газов, диоксида углерода, сероводорода, диоксида серы, сероокиси углерода, предельных и непредельных углеводородов С2–С8, ароматических углеводородов, кислород-, азот-, серосодержащих веществ. Общее их число составило 51. Ключевые слова: высокочистая сера, примеси, идентификация, хромато-масс-спектрометрия, капиллярная колонка.

Main error sources and their contribution to the total error of measuring the optical loss spectrum by the cut-back method are analyzed in the mid-IR range (2-20 mu m) for multimode optical fibers made from materials with high (2-4) refractive index values. It is shown that in case of insufficient fiber length, neglecting the refractive index value leads to a systematic overestimation of the measured optical losses: the higher the refractive index of a fiber core material, the greater an overestimation. The main errors are typically introduced by a bad repeatability of preparation quality of fiber ends and a lower signal-to-noise ratio of mid-IR range experimental setups in comparison with the near-IR range. (C) 2017 Optical Society of America