GeO2 SiO2 Glasses Research Articles

Influence of the core shape on the quality of fiber sensors based on D-shape fiber

Typical optical sensors based on D-shape fibers use standard step-index single-mode fibers (SMF) with a circular core. Multi-mode fibers, fibers with elliptical or rectangular cores, and photonic crystal fibers (PCF) are also used to achieve the best possible sensor performance. However, since the presented sensors differ not only in geometry but, most importantly, in the materials and core sizes, it is difficult to compare their properties directly. In this paper, we numerically analyzed the influence of the shape and size of the core on the sensing performance, with all other relevant parameters being equal. Full Text: PDF References D. Jauregui-Vazquez, J. P. Korterik, C. E. Osornio-Martinez, J. M. Estudillo-Ayala, H. L. Offerhaus, J. A. Alvarez-Chavez, "A strain reflection-based fiber optic sensor using thin core and standard single-mode fibers", Opt. Comm. 522, 128659 (2022). CrossRef H. H. Liu, D. J. Hu, Q. Z. Sun, L. Wei, K. W. Li, C. Liao, B. Li, C. Zhao, X. Dong, Y. Tang, Y. Xiao, G. Keiser, P. Shum, "Specialty optical fibers for advanced sensing applications", Opto-Electron Sci. 2(2), 220025 (2023). CrossRef K. Gasior, T. Martynkien, P. Mergo, W. Urbanczyk, "Fiber-optic surface plasmon resonance sensor based on spectral phase shift interferometric measurements", Sensors and Actuators B: Chemical 257, 602 (2018). CrossRef Y. Ying, G. Si, F. Luan, K. Xu, Y. Qi, H. Li, "Recent research progress of optical fiber sensors based on D-shaped structure", Opt. & Laser Techn. 90, 149 (2017). CrossRef J. Homola, Surface Plasmon Resonance Based Sensors (Berlin, Springer 2006). CrossRef K. Gasior, T. Martynkien., M. Napiorkowski, K. Zolnacz, P. Mergo, W. Urbanczyk, "A surface plasmon resonance sensor based on a single mode D-shape polymer optical fiber", J. Opt. 19, 025001 (2017). CrossRef Q. Wang, W. M. Zhao, "A comprehensive review of lossy mode resonance-based fiber optic sensors", Opt. Lasers in Engineering 100, 47 (2018). CrossRef K. Gasior, T. Martynkien, G. Wojcik, P. Mergo, W. Urbanczyk, "D-shape polymer optical fibres for surface plasmon resonance sensing", Opto-Electron. Rev. 24(4), 209 (2016). CrossRef G. Stepniewski, A. Filipkowski, D. Pysz, J. Warszewski, R. Buczynski, M. Smietana, R. Kasztelanic, "From D-shaped to D-shape optical fiber – A universal solution for sensing and biosensing applications: Drawn D-shape fiber and its sensing applications", Measurement 222, 113642 (2023). CrossRef R. Kasztelanic, H. T. Nguyen, D. Pysz, H. Thienpont, T. Omatsu, R. Buczynski, "Free-Form Optical Fiber with a Square Mode and Top-HatIntensity Distribution", Adv. Science 11, 2402886 (2024). CrossRef J.W. Fleming, "Dispersion in GeO2-SiO2 glasses", Appl. Opt. 23, 4486-4493 (1984). CrossRef T.A. König, P.A. Ledin, J. Kerszulis, M.A. Mahmoud, M.A. El-Sayed, J.R. Reynolds, V.V. Tsukruk., "Electrically Tunable Plasmonic Behavior of Nanocube–Polymer Nanomaterials Induced by a Redox-Active Electrochromic Polymer", ACS Nano 8, 6182-6192 (2014). CrossRef I.Z. Kozma, P. Krok, E. Riedle, "Direct measurement of the group-velocity mismatch and derivation of the refractive-index dispersion for a variety of solvents in the ultraviolet", J. Opt. Soc. Am. B 22, 1479-1485 (2005). CrossRef

Radiation shielding capacity of Li2O-SiO2/GeO2 glasses doped with rare earth oxides: Nuclear security applications

In the present work, the ionizing radiation (namely, gamma-rays, charged particles, and neutrons) attenuation parameters of Li2O–SiO2 (denoted as LS) and Li2O–SiO2–GeO2 glasses doped with Y2O3 and In2O3 (LGY and LGI) glasses were estimated and analyzed with the aim of exploring their shielding potentials. The gamma-ray transmission attenuation coefficient was simulated by the FLUKA code and also estimated by XCOM. Also, the stopping powers and ranges of electrons, protons, α-particles, and carbon ions were estimated for particle kinetic energies within 15–15000 keV. The fast and thermal (25 meV) neutron cross-sections were estimated for the three glasses. At 15 MeV, the mass attenuation coefficient is 0.019, 0.021 and 0.022 cm2/g while the linear attenuation coefficient magnitude varied within the range of 0.047–11.564 cm−1, 0.061–32.008 cm−1 and 0.068–38.122 cm−1 for LS, LGY, and LGI, respectively. The effective atomic number varied from 8.21 to 12.00 for LS, 8.71–22.71 for LGY, and 8.78–26.37 for LGI. Likewise, the charged particle shielding ability of the glasses was in the order: LS < LGY < LGI. This trend was conserved for the neutrons’ cross-sections. Compared to conventional and recently researched shields, LS, LGY, and LGI present viable alternative glass shields in nuclear radiation applications.

Silica-Encapsulated Germania Colloids as 3D-Printable Glass Precursors.

Core–shell colloids make attractive feedstocks for three-dimensional (3D) printing mixed oxide glass materials because they enable synthetic control of precursor dimensions and compositions, improving glass fabrication precision. Toward that end, we report the design and use of core–shell germania–silica (GeO2–SiO2) colloids and their use as precursors to fabricate GeO2–SiO2 glass monoliths by direct ink write (DIW) 3D printing. By this method, GeO2 colloids were prepared in solution using sol–gel chemistry and formed oblong, raspberry-like agglomerates with ∼15 nm diameter primary particles that were predominantly amorphous but contained polycrystalline domains. An ∼15 nm encapsulating SiO2 shell layer was formed directly on the GeO2 core agglomerates to form core–shell GeO2–SiO2 colloids. For glass 3D printing, GeO2–SiO2 colloidal sols were formulated into a viscous ink by solvent exchange, printed into monoliths by DIW additive manufacturing, and sintered to transparent glasses. Characterization of the glass components demonstrates that the core–shell GeO2–SiO2 presents a feasible route to prepare quality, optically transparent low wt % GeO2–SiO2 glasses by DIW printing. Additionally, the results offer a novel, hybrid colloid approach to fabricating 3D-printed Ge-doped silica glass.

Additive Manufacturing of Optical Quality Germania-Silica Glasses.

Direct ink writing (DIW) three-dimensional (3D) printing provides a revolutionary approach to fabricating components with gradients in material properties. Herein, we report a method for generating colloidal germania feedstock and germania-silica inks for the production of optical quality germania-silica (GeO2-SiO2) glasses by DIW, making available a new material composition for the development of multimaterial and functionally graded optical quality glasses and ceramics by additive manufacturing. Colloidal germania and silica particles are prepared by a base-catalyzed sol-gel method and converted to printable shear-thinning suspensions with desired viscoelastic properties for DIW. The volatile solvents are then evaporated, and the green bodies are calcined and sintered to produce transparent, crack-free glasses. Chemical and structural evolution of GeO2-SiO2 glasses is confirmed by nuclear magnetic resonance, X-ray diffraction, and Raman spectroscopy. UV-vis transmission and optical homogeneity measurements reveal comparable performance of the 3D printed GeO2-SiO2 glasses to glasses produced using conventional approaches and improved performance over 3D printed TiO2-SiO2 inks. Moreover, because GeO2-SiO2 inks are compatible with DIW technology, they offer exciting options for forming new materials with patterned compositions such as gradients in the refractive index that cannot be achieved with conventional manufacturing approaches.

Photostability of laser-active centers in bismuth-doped GeO2-SiO2 glass fibers under pumping at 1550 nm.

We report experimental measurements and numerical calculations regarding the photostability of laser-active centers associated with bismuth (BACs) in Bi-doped GeO2-SiO2 glass fibers under pumping at 1550 nm at different temperatures. It was discovered that BACs are unstable under 1550-nm pumping when the temperature is elevated to hundreds of degrees centigrade. A simple numerical model was proposed to account for the discovered instability which turned out to be in good agreement with the experimental data.

Effect of SiO2 on optical properties of bismuth-doped B2O3–GeO2–SiO2 glasses

Bi-doped (60-x)GeO2–xSiO2–15B2O3–20MgO–5Al2O3–0.5Bi2O3 (x = 0, 5, 10, 15,20, 25 mol%)glasses were prepared by a conventional melt-quenching process. A broad near-infrared (NIR) photoluminescence (PL) band from Bi centers centered around 1100 nm with a large full-width-at-half-maximum value (~ 195 nm) was observed under excitation at 700 nm. Along with the increase of SiO2 concentration, the NIR PL intensity and the quantum yield (44.1–51.2%) increase first and then decrease, and the PL lifetime increases from 409 to 464 µs. The spectroscopic properties can be interpreted in terms of Bi centers with different valence states, which were confirmed by two-dimension photoluminescence excitation map spectra. The dependence of optical properties on SiO2 concentration is mainly attributed to the change of the optical basicity among different samples. This Bi-doped B2O3–GeO2–SiO2 glass could find potential application in fiber amplifier and laser due to the efficient and tunable broad NIR luminescence.

Nanoscale Phase-Separated Structure in Core-Shell Nanoparticles of SiO2-Si1-xGexO2 Glass Revealed by Electron Microscopy.

SiO2-based optical fibers are indispensable components of modern information communication technologies. It has recently become increasingly important to establish a technique for visualizing the nanoscale phase-separated structure inside SiO2-GeO2 glass nanoparticles during the manufacturing of SiO2-GeO2 fibers. This is because the rapidly increasing price of Ge has made it necessary to improve the Ge yield by clarifying the detailed mechanism of Ge diffusion into SiO2. However, direct observation of the internal nanostructure of glass particles has been extremely difficult, mainly due to electrostatic charging and the damage induced by electron and X-ray irradiation. In the present study, we used state-of-the-art scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and energy dispersive X-ray spectroscopy (EDX) to examine cross-sectional samples of SiO2-GeO2 particles embedded in an epoxy resin, which were fabricated using a broad Ar ion beam and a focused Ga ion beam. These advanced techniques enabled us to observe the internal phase-separated structure of the nanoparticles. We have for the first time clearly determined the SiO2-Si1-xGexO2 core-shell structure of such particles, the element distribution, the degree of crystallinity, and the quantitative chemical composition of microscopic regions, and we discuss the formation mechanism for the observed structure. The proposed imaging protocol is highly promising for studying the internal structure of various core-shell nanoparticles, which affects their catalytic, optical, and electronic properties.

Influence of valence state of copper ions on structural and spectroscopic properties of multi-component PbO–Al2O3–TeO2–GeO2–SiO2 glass ceramic system- a possible material for memory switching devices

Multi-component glass ceramics with composition 29PbO–5Al2O3–1TeO2 –10GeO2– (55–x) SiO2 doped with different concentrations of CuO (0 ≤ x ≤ 1.0 mol %) were synthesized by melt quenching technique and subsequent heat treatment. These glass ceramics were characterized by X–ray diffraction, scanning electron microscope, differential thermal analysis, optical absorption, electron paramagnetic resonance, Fourier transform infrared and Raman studies. The absorption spectra of these glass ceramics exhibited a broad absorption band in the range 650–950 nm which is ascribed to 2B1g → 2B2g octahedral transition of Cu2+ ions. A feeble band around 364 nm is also identified in the samples doped with CuO up to 0.6 mol% as being due to charge transfer between the two oxidation states Cu2+ and Cu+ of copper ions. The EPR spectrum recorded at room temperature exhibited a strong resonance signal at g⊥ = 2.072 and a shallow quadruplet at about gǁ = 2.401. FTIR and Raman spectra of the titled samples provide significant information about various structural units viz., silicate, germanate, PbO4, PbO6, AlO6, TeO4 and TeO3 that are present in these ceramic matrix. Analysis of the spectroscopic investigations reveals that with an increase in the concentration of CuO up to 0.6 mol% copper ions do exist in Cu2+ and Cu+ states and they act as modifiers and net work formers respectively. Therefore, glass ceramic sample contains 0.6 mol% of CuO is favorable for memory switching action.

The dependence of Raman defect bands in silica glasses on densification revisited

This paper focuses on the densification signature measured by Raman spectroscopy in silica-based glasses. We have studied a pure silica glass and a 25GeO2–75SiO2 binary glass fabricated by plasma chemical vapor deposition (PCVD), using the fictive temperature T f as a variable parameter ranging from 950 to 1400 °C. Macroscopic density measurements highlighted two opposite behaviors: the higher the fictive temperature, the lower the density of the GeO2–SiO2 glass, in contrast to what is observed in the pure silica glass. Yet, Raman spectra of both these glasses showed similar trends: the intensities of the two defect bands, D1 and D2, increase with increasing fictive temperature. Therefore, the D1 and D2 bands cannot be used as a reliable signature of densification in binary glasses.

Photoluminescence characteristics and energy transfer between Bi3+ and Eu3+ in Na2O—CaO—GeO2—SiO2 glass

We report the photoluminescence (PL) of Eu3+-doped glass with Bi3+ as a sensitizer. The specific glass system with the strong enhancement of the red emission of Eu3+ is obtained by adding a small number of Bi3+ ions instead of increasing the Eu3+ concentration. The emission band of Bi3+ overlaps with the excitation band of Eu3+ and the lifetime decay curves, resulting in a very efficient energy transfer from Bi3+ to Eu3+. The probability of energy transfer is strongly dependent on Bi3+ concentration. In addition, the intensity of 4f–4f transition is much stronger than that of a charge-transfer (CT) band in the excitation spectrum, which indicates that the Na2O—CaO—GeO2-SiO2 glass is a suitable red-emitting phosphor with high stability as a candidate for light-emitting diodes (LEDs).

Short and medium range order in two-component silica glasses by positron annihilation spectroscopy

The dependence of chemical composition on the average sizes of subnanometer-scale intrinsic structural open spaces surrounded by glass random networks in two-component silica-based glasses was investigated systematically using positronium (Ps) confined in the open spaces. The average sizes of the open spaces for SiO2-B2O3 and SiO2-GeO2 glasses are only slightly dependent on the chemical compositions because the B2O3 and GeO2 are glass network formers that are incorporated into the glass network of the base SiO2. However, the open space sizes for all SiO2-R2O (R = Li, Na, K) glasses, where R2O is a glass network modifier that occupies the open spaces, decrease rapidly with an increase in the R2O concentration. Despite the large difference in the ionic radii of the alkali metal (R) atoms, the open space sizes decrease similarly for all the alkali metal atoms studied. This dependence of the chemical composition on the open space sizes in SiO2-R2O observed by Ps shows that the alkali metal atoms do not randomly occupy the structural open spaces, but filling of the open spaces by R2O proceeds selectively from the larger to the smaller open spaces as the R2O concentrations are increased.

Novel method of glasses SiO2-GeO2 preparation monitoring

Kinetic spectrophotometric analysis of germanium and silicon in aqueous alcohol without their separation or concentration is an important analytical issue, as such systems have been widely applied in the sol–gel synthesis of SiO2–GeO2 glasses, the technology to introduce varied concentrations of germanium to the silicon matrix. Of extreme interest is the initial stage of copolycondensation of germanium and silicon compounds; to a great extent, it determines the properties of the final product. The proposed method can be applied to other Siand Ge-containing systems [1].

Effect of composition on Bi2O3–SiO2–GeO2 glass properties

Glasses with composition Bi4(SixGe 1– x )3O12, where x = 0.33, 0.5 and 0.06, were obtained by melting for 30 min and two-step melting. Their characteristic temperatures, densities, refractive indices and microhardness were determined and the composition dependences studied. Glasses in the system Bi 2 O 3 –GeO 2 –SiO 2 are used in optics, electronics, and the telecommunications industry as laser materials when doped with rare-earth elements and as cryogenic charged-particle detectors when reduced in a hydrogen atmosphere. The possibility using these glasses as a basis to obtain glass ceramic materials with scintillation properties is of greatest interest, since many sensitive scintillation elements currently used have a number of substantial drawbacks. For example, NaI and LiI crystals are hygroscopic, which causes instruments to malfunction; CsI is nonhygroscopic but it is unstable under high irradiation doses, which sharply curtails its applicability. ZnS single crystals cannot be used to detect -radiation because of the lose transmission in the visible range. The range of application of single-crystal KI is limited by the presence of 40 K in it. In addition, each material mentioned above requires activating additives, which are required in order for it to scintillate. In this light there is promise in using single crystals with the structure of eulytin (Bi4X3O12, where X = Si, Ge) as the active element, since the centers of emission are bismuth ions, making activators unnecessary. For equal volumes BGO and BSO crystals show higher photon detection efficiency than other scintillation crystals. The undoubted advantages of eulytins are their mechanical properties and nonhygroscopicity. In view of the difficulties arising in growing eulytin crystals, which greatly increase production costs, a step forward is the use of glass ceramic materials based on glasses with equivalent composition. Matrix glasses are produced using well-perfected classic technologies, and glass ceramic materials can be obtained from them by easily accessible methods — heat treatment or laser irradiation. Transparent glass ceramic materials based on glass with the compositions 2Bi 2 O 3 ;3SiO 2 and 2Bi 2 O 3 ;3GeO 2 , containing up to 70% eulytin crystallites and possessing scintillation properties close to those single crystals, have now been obtained. As in the case of single crystals these properties of bismuth-germanate glass ceramics are higher while the radiation resistance is lower than for bismuth-silicate. In turn, bismuth-silicate glass ceramic is characterized by the opposite properties (the scintillation properties are lower but the radiation resistance is higher) [1]. Therefore, combining the useful properties of both materials in a single material is a topical problem. Most works are devoted to studying phase equilibria in the binary systems Bi2O3–GeO2 and Bi2O3–SiO2. The ternary system Bi 2 O 3 –GeO 2 –SiO 2 has been less studied. Glass formation in the indicated system was studied in [2]: the characteristic temperatures were determined, nontransparent glass ceramic materials based on these glasses were obtained, and the composition of the crystallizing phases and the lattice parameters of the crystals formed were determined.

Nickel-assisted growth and selective doping of spinel-like gallium oxide nanocrystals ingermano-silicate glasses for infrared broadband light emission

The target of taking advantage of the near-infrared light-emission properties of nickelions in crystals for the design of novel broadband optical amplifiers requires theidentification of suitable nanostructured glasses able to embed Ni-doped nanocrystalsand to preserve the workability of a glass. Here we show that Ni doping ofLi2O–Na2O–Ga2O3–GeO2–SiO2 glass (with composition 7.5:2.5:20:35:35 and melting temperature1480 °C, sensibly lower than in Ge-free silicates) enables the selective embedding of nickel ions inthermally grown nanocrystals of spinel-like gallium oxide. The analysis of transmission electronmicroscopy and x-ray diffraction data as a function of Ni-content (from 0.01 to 1 mol%) indicatesthat Ni ions promote the nanophase crystallization without affecting nanoparticle size (∼6 nm) andconcentration (∼4 × 1018 cm − 3). Importantly, as shown by optical absorption spectra, all nickel ions enter into the nanophase, with anumber of ions per nanocrystal that depends on the nanocrystal concentration and ranges from 1 to102. Photoluminescence data indicate that fast non-radiative decay processes become relevantonly at mean ion–ion distances shorter than 1.4 nm, which enables the incorporation of afew Ni ions per nanoparticle without too large a worsening of the light-emission efficiency.Indeed, at 0.1 mol% nickel, the room temperature quantum yield is 9%, with an effectivebandwidth of 320 nm.

On the natures of radiation-induced point defects in GeO_2-SiO_2 glasses: reevaluation of a 26-year-old ESR and optical data set

26-year-old electron spin resonance (ESR) and optical data pertaining to isochronal annealing studies of x-ray induced defect centers in a GeO2-SiO2 glass are revisited here with the object of extracting new insights regarding the fundamental natures of these defects. It is concluded that (i) the paramagnetic Ge(1) and Ge(2) centers are two energetically inequivalent configurations of a single trapped-electron defect, in analogy to what is known to be the case for the Ge(II) and Ge(I) centers respectively in α quartz [Isoya et al., J. Chem. Phys. 69, 4876 (1978)], and (ii) the germanium lone pair center (GLPC) stably traps holes only in pairs and hence remains ESR silent.

Structure and property of multicomponent germanate glass containing Y2O3

CaO–BaO–Al2O3–SiO2–GeO2 glasses doped with 0·00–16·67 wt-% Y2O3 have been prepared by conventional melt quenching method. The influence of Y2O3 addition on the properties and structure of the glasses has been investigated. The results show that, with the introducing of Y2O3, the density, glass transition temperature and thermal expansion coefficient of the glass increase but the chemical durability declines. In addition, compared with the glass without Y2O3, the bend strength of the glass including 4·76 wt-% Y2O3 increased from 54 to 110 Mpa. The possible mechanism is that yttria acts as a network former in the structure and makes the island shape network unit repolymerisation by forming Ge–O–Y bond. The absorption strength caused by hydroxyl vibration decreased up to completely disappearance as the Y2O3 content increased continuously. The introducing of yttria in the composition causes the conversion from four coordination to higher coordination germanium, which decreases non-bridge oxygen (NBO) and weakens hydroxyl characteristic absorption.

The structure of GeO2–SiO2 glasses and melts: A Raman spectroscopy study

We have investigated a series of glasses and melts along the GeO 2 –SiO 2 join using in situ Raman spectroscopy. The results for both the glasses and melts are consistent with a continuous random network in which there are ‘regions’ that are SiO 2 -like, GeO 2 -like and mixed GeO 2 –SiO 2 -like. Incorporation of GeO 2 into the SiO 2 network is initially accommodated via the 3- and 4-membered SiO 4 rings which are lost as they convert to larger mixed Ge/Si rings. The LO–TO mode behavior is also consistent with a network that is composed of different ‘regions’ and is similar to that expected from the Bruggeman effective media model. At the highest temperatures there are indications that the mixed Ge/Si rings convert back to small 3-membered GeO 4 rings and large SiO 4 rings; the small 3- and 4-membered SiO 4 rings are not reformed.

The structure of SiO2–GeO2 glasses: A spectroscopic study

Four glasses of the SiO2–GeO2 binary system have been synthesized via a sol–gel route followed by a heat treatment and a quench. Glass structure has been determined by Ge K-edge X-ray absorption spectroscopy (XAS) at low temperature and Raman spectroscopy. These mixed glasses present a continuous random network of interconnected GeO4 and SiO4 tetrahedra, with GeO4 tetrahedra similar to the GeO4 units in GeO2 glass and continuous compositional variations from GeO2-rich regions to SiO2-rich regions. Such a random mixture is consistent with physical properties of these binary glasses as well as with the chemical dependence of their polyamorphism at high pressure. This EXAFS-derived mean Ge–O–Si angles are close to the Ge–O–Ge mean angle in GeO2 glass, 134° and 130°, respectively. This misfit with the Si–O–Si angles might explain the ease of formation of isolated and pair defects centers, which are suspected to be at the origin of photo-induced modifications of optical properties in Ge-bearing SiO2 glasses.

Precipitation of Ge nanoparticles from GeO2 glasses in transmission electron microscope

We show, using spatially resolved energy loss spectroscopy in a transmission electron microscopy (TEM), that GeO2 and GeO2–SiO2 glasses are extremely sensitive to high energy electrons. Ge nanoparticles can be precipitated in GeO2 glasses efficiently by the high-energy electron beam of a TEM. This is relevant to TEM characterization of luminescent Ge nanoparticles in silicate glasses, which may produce artificial results.

Ge coordination states in SiO2-GeO2 glasses at high pressure, inferred from in situ XAFS at the Ge K-edge

In SiO2-GeO2 glasses submitted to high pressure conditions, germanium atoms undergo a coordination change from four to six on a pressure-range depending on the composition. In the transition region, the possibility of having a mixture of tetrahedra and octahedra for Ge instead of the intermediate fivefold coordination state has been studied. Through comparison of the informations extracted from XANES and EXAFS, the model of a mixture of IV and VI coordination states, with a possible small amount of fivefold coordinated Ge appearing on the compression, is favoured.