E. B. Kryukova

Chalcogenide glasses doped with Tb, Dy and Pr ions

Abstract Optically homogeneous As–Se and As–S–Se glasses doped with the ions of rare-earth elements (REE), i.e. praseodymium, dysprosium and terbium up to 9000 wt. ppm were synthesized. A technique for introduction of REE into chalcogenide glasses (CG) is based on solidification of the melt of glass-forming compounds with the dopants of REE iodide and the time–temperature modes minimizing glass crystallization and dopant clustering. Microhomogeneity and absorption of the produced samples of the doped glasses were studied in the middle IR range. A spectral dependence of absorption by REE ions was investigated and the extinction coefficients were determined for the most intensive absorption bands of the ions of praseodymium, dysprosium and terbium. Luminescence properties of CG doped with Tb3+ were investigated at 4–5 μm. The optical fibers based on arsenic selenide doped with terbium were manufactured with optical losses of 1.5 dB/m at 6–9 μm and a bending strength of 0.6 GPa.

Effect of Oxygen Impurity on the Optical Transmission of As2Se3.4Glass

As2Se3.4glass samples with controlled oxygen content in the range (1.4–7.9) × 10–2wt % were used to assess the effect of oxygen impurity on the IR absorption spectrum of the glass. The spectral dependence of the extinction coefficient for oxygen impurity was determined in the range 600–1400 cm–1. It was shown that the presence of 10–5wt % O gives rise to additional losses comparable to the intrinsic losses in the CO2lasing range.

Hydroxyl groups in phosphosilicate glasses for fibre optics

Abstract IR absorption spectra of phosphosilicate glasses containing 1–19 mol% of P2O5 are measured and analyzed. Interaction of hydroxyl groups with the phosphorus centres in the phosphosilicate glass is investigated in cluster models using PM3 and MNDO quantum-chemical methods. An explanation of the experimentally observed change of vibrational absorption bands caused by the hydroxyl groups is proposed.

Solubility of nitrogen, carbon, and hydrogen in FeO–Na2O–Al2O3–SiO2 melt and liquid iron alloy: Influence of oxygen fugacity

Abstract—Reactions of nitrogen, carbon, and hydrogen with FeO–Na2O–Al2O3–SiO2 melts, liquid iron alloys, and graphite were investigated at 4 GPa, 1550°C, and fO2 values 1.5–3.0 orders of magnitude below fO2(IW). A number of features important for the understanding of the formation conditions of volatile nitrogen compounds during melting of the Earth’s early reduced mantle were revealed. The nitrogen content of melt increases with decreasing fO2 from 0.96 wt % at ΔlogfO2(IW) =–1.4 to 4.1 wt % at ΔlogfO2(IW) =–3.0, whereas the hydrogen content of melt is weakly dependent on fO2 and lies within 0.40–0.47 wt %. The carbon content is approximately 0.3–0.5 wt %. The IR and Raman spectroscopy of the glasses indicated that the dissolution of nitrogen, carbon, and hydrogen in silicate liquids is accompanied by the formation of NH3, N2, and CH4 molecules, as well as NH2–, NH2+, NH4+ and CH3– complexes. Hydrogen is dissolved in melts as OH–, H2O, and H2. The experiments also demonstrated the presence of species with C=O double bonds in the melts. It was found that the solubility of nitrogen in FeO–Na2O–Al2O3–SiO2 melts increases in the presence of carbon owing to the formation of species with C–N bonds in the silicate liquid. One of the most remarkable features of nitrogen, carbon, and hydrogen interaction with FeO–Na2O–Al2O3–SiO2 melts is a significant change in the proportions of N–C–H–O species at fO2 2–3 orders of magnitude below fO2(IW). Under these conditions, a sharp decrease in the contents of NH4+, NH2+ (O–NH2), OH, H2O, and CH4 is accompanied by enrichment in NH2– (=Si–NH2) and NH3. As a result, NH3 becomes the dominant nitrogen species in the melt. The investigation revealed high nitrogen solubility in iron alloys at fO2 < fO2(IW). The nitrogen content increases from 2.47 wt % at ΔlogfO2(IW) =–1.4 to 3.63 wt % at ΔlogfO2(IW) =–3.0. The carbon content of N–C–Fe alloys ranges from 2.3 to 3.8 wt % and decreases with decreasing fO2. The siderophile behavior of nitrogen at fO2 < fO2(IW) suggests that part of nitrogen could be dissolved in iron alloys during large-scale melting of the early reduced mantle with subsequent nitrogen burial in the Earth’s metallic core. It was suggested that the self-oxidation of magmas in the Earth’s early mantle with the release of reduced N–C–H–O volatiles could be one of the reasons of extensive nitrogen degassing.

Solution behavior of C-O-H volatiles in FeO-Na 2 O-Al 2 O 3 -SiO 2 melts in equilibrium with liquid iron alloy and graphite at 4 GPa and 1550°C

In order to elucidate the solution behavior of carbon and hydrogen in iron-bearing magmatic melts in equilibrium with a metallic iron phase and graphite at oxygen fugacity (fO2) values 2–5 orders of magnitude below the iron-wustite buffer equilibrium, fO2 (IW), experiments were carried out at 4 GPa and 1550°C with melts of FeO-Na2O-SiO2-Al2O3 compositions. Melt reduction in response to an fO2 decrease was accompanied by a decrease in FeO content. The values of fO2 in the experiments were determined on the basis of equilibrium between Fe-C-Si alloy and silicate liquid. Infrared and Raman spectroscopy showed that carbon compounds are formed in FeO-Na2O-SiO2-Al2O3 melts: CH4 molecules, CH3 complexes (Si-O-CH3), and complexes with double C=O bonds. The content of CO2 molecules and carbonate ions (CO32−) is very low. In addition to carbon-bearing compounds, dissolved hydrogen occurs in melt as H2 and H2O molecules and OH− groups. The spectral characteristics of FeO-Na2O-SiO2-Al2O3 glasses indicate the occurrence of redox reactions in the melt, which are accompanied at decreasing fO2 by a significant decrease in H2O and OH−, a slight decrease in H2, and a significant concomitant increase in CH4 content. The content of species with the double C=O bond increases considerably at decreasing fO2 and reaches a maximum at ΔlogfO2(IW) = −3. According to the obtained IR spectra, the total water content (OH− + H2O) in the glasses is 1.2–5.8 wt % and decreases with decreasing fO2. The high H2O contents are due largely to oxygen release related to FeO reduction in the melt. The total carbon content at high H2O (4.9–5.8 wt %) is approximately 0.4 wt %. The carbon content in liquid iron alloys depends on silicon content and, probably, oxygen solubility and ranges from 0.3 to 3.65 wt %. Low carbon contents were observed at a significant increase in Si content in liquid iron alloy, which may be as high as ∼13 wt % at fO2 values 4–5 orders of magnitude below fO2(IW).

Refractive index spectral dependence, Raman spectra, and transmission spectra of high-purity Si28, Si29, Si30, and Sinat single crystals

Precise measurement of the refractive index of stable silicon isotopes Si, Si, Si single crystals with enrichments above 99.9 at.% and a silicon single crystal Si of natural isotopic composition is performed with the Fourier-transform interference refractometry method from 1.06 to more than 80 μm with 0.1 cm resolution and accuracy of 2 × 10 . . . 1 × 10. The oxygen and carbon concentrations in all crystals are within 5 × 10 cm and the content of metal impurities is 10 . . . 10 at.%. The peculiar changes of the refractive index in the phonon absorption region of all silicon single crystals are shown. The coefficients of generalized Cauchy dispersion function approximating the experimental refractive index values all over the measuring range are given. The transmission and Raman spectra are also studied.We performed precise measurement of the refractive index of stable silicon isotopes 28Si, 29Si, and 30Si single crystals with enrichments above 99.9 at.% and a silicon single-crystal natSi of natural isotopic composition with the Fourier-transform interference refractometry method from 1.06 to more than 80 μm with 0.1 cm(-1) resolution and accuracy of 2×10(-5)…1×10(-4). The oxygen and carbon concentrations in all crystals are within 5×10(15) cm(-3), and the content of the metal impurities is 10(-5)…10(-6) at.%. The peculiar changes of the refractive index in the phonon absorption region of all silicon single crystals are shown. The coefficients of the generalized Cauchy dispersion function approximating the experimental refractive index values all over the measuring range are given. The transmission and Raman spectra are also studied.

Spectral dependence of the refractive index of single-crystalline GaAs for optical applications

The refractive index of crystalline GaAs is measured by the method of interference refractometry in the wavenumber range from 10?500 to 540?cm?1 (or the wavelength range from 0.9 to 18.6??m) with a resolution of 0.1?cm?1. The measurement results are approximated by the generalized Cauchy dispersion formula of the 8th power. Spectral wavelength dependences of the first- and second-order derivatives of the refractive index are calculated, and the zero material dispersion wavelength is found to be ?0 = 6.61??m. Using three GaAs plates of different thicknesses we managed to raise the refractive index measurement accuracy up to 4 ? 10?4 or 0.02%, being nearly by an order of magnitude better than the data available.

Precise measurement of refractive index spectral dependence of optical materials for laser, fiber, and integrated optics

An interferometric technique for measuring the spectral dependence of the refractive index of solid-state materials to an accuracy of 10−5 over the entire transparency region is described. The possibilities of the technique are demonstrated by the example of new phosphate glasses formulated for laser and fiber optics. It is shown that, in the presence of absorption bands in the transmission spectrum, the technique allows their associated jumps in the refractive index values to be recorded on the order of 10−4−10−5 and below. The shift in the spectral dependence of the refractive index in the region of the absorption band with intensity at 1.7 cm−1 is measured for the first time.

Spectral dependence of the refractive index of chemical vapor deposition ZnSe grown on substrate with an optimized temperature increase

Precise measurement of the refractive index of chemical vapor deposition (CVD) ZnSe with the Fourier-transform interference refractometry method from 0.9 to 21.7microm (from 11,000 to 460cm(-1)) with 0.1cm(-1) resolution is described. For this measurement, structurally homogeneous ZnSe plates were grown on a substrate with an optimized temperature increase. Using three ZnSe plates of different thicknesses, we managed to raise the measurement accuracy of the refractive index up to 2x10(-5) (being nearly 1 order of magnitude better than the available data) in the near IR and most of the middle IR wavelength range from 0.9 to 12.5microm (wavenumber range of 11,000-800cm(-1)) and up to 1...4x10(-4) in the 12.5-21.7microm (800-460cm(-1)) region. The experimental results are approximated by a generalized Cauchy dispersion function of the 8th power. Spectral wavelength dependencies of the first- and second-order derivatives of the refractive index are calculated, and the zero material dispersion wavelength is found to be lambda(0)=4.84microm.

Effect of SO2 impurity on the optical transmission of As2S3 glass

To assess the effect of sulfur dioxide impurity on the optical properties and absorption spectrum of glassy arsenic sulfide, we have prepared As2S3 glass samples containing 0.01 to 0.12 wt % SO2 and have measured their transmission spectra in the range 500–5000 cm−1. The extinction coefficient of sulfur dioxide in glassy arsenic sulfide, evaluated from the intensity of the 1158-cm−1 absorption band, is 10.0 ± 0.7 cm−1/wt%.