Heavy Metal Fluoride Glasses Research Articles

Optical properties of rare-earth-doped HMF glasses

Physical, optical properties and emission characteristics of heavy metal fluoride (HMF) glasses containing 1 mol% of Pr, Nd and Tb as dopants are reported. Room temperature absorption spectra have been determined from VIS to the NIR. Photoluminescence spectra were recorded at 300 and 77 K to measure the stimulated emission cross-section of the laser transitions employing an Ar + (487.9 nm) laser. The quantum efficiencies of the fluorescent levels of these optical glasses were determined from measured lifetimes of the recorded luminescent levels at room and liquid nitrogen temperatures.

Thermal lensing in heavy metal fluoride glasses

The effect of glass composition on the theoretical thermal lensing of a ZrF 4 BaF 2 LaF 3 AlF 3 NaF (ZBLAN) heavy metal fluoride glasses (HMF) has been examined. A number of composition substitutions, i.e., HfF 4 for ZrF 4 , PbF 2 for BaF 2 , and LiF and NaCl for NaF, have been made, and the effects of these substitutions on critical properties have been determined. These substitutions have significant effects on the refractive index, coefficient of thermal expansion (CTE), and the thermo-optic coefficient (d n /d T ). The changes in properties can be used to develop glass compositions that will show no thermal lensing when heated by laser fluences. The elimination of thermal lensing by composition changes is evaluated in terms of changes in heat capacity, glass stability and processing parameters that might be detrimental to large scale window production.

An EPR microwave saturation study of Co 2+ in a zirconium fluoride-based glass

Optical and electron paramagnetic resonance (EPR) spectroscopies have been used to investigate the coordination number and site symmetry of Co 2+ in a heavy metal fluoride glass. From EPR microwave saturation measurements, the zero field splitting of the Co 2+ ion doped into a ZBL glass was determined. It was deduced from this that the Co 2+ resides in a site of cubic symmetry.

Manufacture of fluoride glass preforms

Since vapour deposition methods for heavy metal fluoride glasses are still in the early stages of development, preforms are prepared by pouring two slightly different glass melts sequentially into a heated mould. In this paper, a shutter technique is described, which has been used to make both doped and undoped preforms, and which facilitates the production of more complex fibre structures.

Fluoride glasses: synthesis and properties

The discovery of heavy metal fluoride glasses has opened new prospects for fiber optics operating beyond 2 pm with expected losses less than 1od2 dB/Km. The main interest of fluoride glasses lies in their infrared transmission up to 8 pm in the bulk form and 4.5 pm for optical fibers. We have reported here the preparation, the glass forming systems and properties of heavy metal fluoride glasses. The development of optoelectronic devices and systems for tel~communications, sensing and miscellaneous application~ has stimulated intense research on vitreous materials. Insofar as it becomes possible to reach the theoretit:al limits of silica-based glasses, further improvements in performances depend only on the discovery of new glasses and their optimization. The discovery of uiiexpected glases at Rennes University in 1974l was tlie beginning of numerous researches on fluoride and, more generally, halide glasses, resulting in the description of hundreds of new glass forming systen~. Fluor de glass fiber technology was investigated, especially in its specific aspects. Glass formation, which was considered as an exceptional event, appears now as a common f\:ature in many fluoride systems. This development has expanded the horizons of the traditional field of glass science. Also, infrared fibers are now available for vari~s technical purposes. Prospects for long haul repeaterless telecommunications are promising, in spite of extrinsic scattering losses which keep the actua1 losses al~ove the theoretical limits. The closest applications of fluoride glasses in this field of telecommunications relate to optical amplification, as they offer possibilities st the 1.31 micrometer wavelength 2 .

酸素イオン注入による重金属フッ化物ガラス耐水性の改善

A typical heavy metal fluoride glass composed of 53ZrF4-20BaF2-4LaF3-3AlF3-20NaF in molar percentage was implanted with 15keV oxygen ions to the dose of 2×1017ions/cm2. The ion implantation did not affect the transmission spectra of the glass in the infrared or visible region in any detectable extent, although it did give rise to a slight drop at the ultraviolet edge. The surface layer fabricated by ion implantation exhibited excellent chemical durability which protected the glass from being corroded by water. Surface characterizations by RBS and XPS revealed that an oxyfluoride layer was formed on the glass surface and it is concluded that this compositional modification is responsible for the improvement in the water durability of the glass.

Vibrational spectra in fluoride crystals and glasses at normal and high pressures by computer simulation

Molecular dynamics computer simulation methods to obtain the infrared and Raman spectra of ionic liquids and glasses are described. These methods are applied to two problems: (1) the simulation and interpretation of the vibrational spectra of heavy metal fluoride glasses, and (2) the problem of reversible collapse of network glasses and the dramatic spectroscopic consequences of this collapse observed in recent experiments on SiO 2-like glasses. As a contribution to this latter problem, the case of BeF 2, for which our rigid ion potentials should be good approximations to the actual interactions, is studied. In the spectra, an initial network stiffening with increase of pressure, followed by rather sudden collapse to a spectrum characteristic of a higher coordinated state, is observed. This is correlated with a sudden increase in average coordination numbers. The changes are mostly reversible on decompression, so the behavior is reminiscent of the transition between ‘vitreous polymorphs’ observed in the case of vitreous water and vitreous silica.

Removal of Surface Carbon Impurities from Ultra-Low Loss Fluoride Glasses

ABSTRACTThis paper describes a novel route for removal of surface carbon from heavy-metal fluoride glasses melted in vitreous carbon crucibles. The technique utilizes dry etching with active fluorine produced in a NF3 plasma generated in a microwave cavity.

Fluorescence characteristics of Nd 3+ -doped heavy metal fluoride glasses

This paper reports the preparation of (1 M%) NdF 3 doped ZrF 4AlF 3 BaF 2RF (RF = LiF, NaF and KF) and their physical, absorption and photoluminescence properties at 300 and 77K. the radiative properties, stimulated emission cross-section, quantum efficiencies of the lasing transition ( 4 F 3 2 → 4 I 11 2 ) at 1.05 μm have been measured by using an Ar + laser as the source of excitation.

ChemInform Abstract: Preparation and Analysis of High‐Purity Materials for Low Loss Heavy Metal Fluoride Glasses

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Preparation and Analysis of High‐Purity Materials for Low Loss Heavy Metal Fluoride Glasses.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Interferometric method for concurrent measurement of thermo-optic and thermal expansion coefficients

A Fabry-Perot-type interferometer is described that permits the concurrent measurement of the coefficient of thermal expansion (alpha) and the thermooptic coefficient (dn/dT) of transparent materials. Measurements of the a and the dn/dT of vitreous silica and a heavy-metal fluoride glass show that the technique is accurate, reproducible, and easily performed. In addition, the technique is used to show that the dn/dT of heavy-metal fluoride glasses is negative and temperature dependent. The magnitude of dn/dT is found to increase with increasing temperature.

Separation of intrinsic and extrinsic optical absorption in a fluoride glass

The contribution of impurity ions to the total optical absorption of a heavy metal fluoride glass has been determined at 532 and 1064 nm. Four ZrF4-BaF2-LaF3-AlF3-NaF glasses were prepared from various purity raw materials. The absorption coefficients of these glasses range from 0.92 to 45.4×10−4 cm−1 at 1064 nm and from 7.43 to 11.1×10−4 cm−1 at 532 nm as determined by laser calorimetry. The concentrations of Fe, Ni, Cu, and Co ions in each glass were determined by graphite furnace atomic absorption spectroscopy. These two measurements enable the absorption, due to transition metal ions to be differentiated from the intrinsic absorption of the glass. At 1064 nm, the absorption coefficient of these glasses is controlled entirely by the transition metal ion content. However, at 532 nm, the absorption by the transition metal ions accounts for 4–42% of the total absorption depending on impurity concentration. The intrinsic absorption of this fluoride glass calculated from these data at 532 nm is (7.69±0.99)×10−4 cm−1.

Computer-simulation analysis of the ESR spectra of V-type centers in irradiated heavy-metal fluoride glasses.

Computer line-shape simulations were carried out on the electron-spin-resonance spectra of several heavy-metal fluoride glasses following exposure to ioniziong radiation at cryogenic temperatures. The primary objects of this study were certain spectra circumstantially attributable to holes trapped on a cluster of two or more inequivalent fluoride or foreign halide ions. The earlier attribution of certain spectral features to ${\mathrm{FCl}}^{\mathrm{\ensuremath{-}}}$ and ${\mathrm{FBr}}^{\mathrm{\ensuremath{-}}}$ species was confirmed in Cl- and Br-doped glasses, respectively, although the simulations show that ${\mathrm{FCl}}^{\mathrm{\ensuremath{-}}}$ in the glasses has a structure quite different from the same species in mixed alkali halide crystals. Two other spectra---universally observed in irradiated glasses composed of ${\mathrm{ZrF}}_{4}$ (or ${\mathrm{HfF}}_{4}$), ${\mathrm{BaF}}_{2}$, and virtually any number of other fluoride constituents---were also examined in detail. The previous assignment of one of these spectral components to ${\mathrm{F}}_{2}^{\mathrm{\ensuremath{-}}}$ molecular ions is sustained, although the specific nature of these defects is now argued to be interstitial fluorine atoms in configurations analogous to ${\mathit{V}}_{\mathit{K}\mathit{A}}$ and ${\mathit{V}}_{\mathit{H}}$ centers (rather than ${\mathit{V}}_{\mathit{K}}$ centers) in the alkaline-earth fluorides. The second ubiquitous component, which was previously ascribed to ``interstitial ${\mathit{F}}^{0}$,'' is demonstrated to arise from an ${\mathrm{F}}_{3}^{2\mathrm{\ensuremath{-}}}$ species similar to the ${\mathit{V}}_{\mathit{t}}$ center in LiF. The ${\mathrm{F}}_{2}^{\mathrm{\ensuremath{-}}}$ and ${\mathrm{F}}_{3}^{2\mathrm{\ensuremath{-}}}$ can be thought of as ``on-center'' and ``off-center'' configurations of the interstitial fluorine atom, and it appears that the former may undergo a thermal transmutation into the latter.

Heterogeneous Plantinum Nucleation and Crystallization of a Heavy‐Metal Fluoride Glass

The effect of controlled heterogeneous nucleation by platinum on the crystallization of a ZrF4‐BaF2‐LaF3‐AlF3‐NaF (ZBLAN) glass was studied. Various levels of platinum were incorporated into this glass by a combination of PtCl2‐doping and melting‐atmosphere variation. The effect of doping levels and melting conditions on the incorporation of platinum and the subsequent nucleation of crystals was studied by optical microscopy, scanning electron microscopy, differential scanning calorimetry (DSC), and X‐ray diffraction. Increased platinum in the glass resulted in an increased number of nucleation sites for the growth of β‐ZrF4‐BaF2 crystals. Analysis of isothermal and ramp‐rate DSC measurements indicated that the crystallization of this glass changed from surface controlled to bulk controlled with an increased number of nuclei. This was confirmed by optical microscopy. In addition, Avrami analysis of the isothermal crystallization data gave an accurate approximation of the number of nuclei in the glass.

Intensity-dependent upconversion efficiencies of Er3+ ions in heavy-metal fluoride glass

The upconversion of infrared radiation to shorter wavelengths by Er3+ ions in heavy-metal fluoride glasses, some doped with Yb3+, has been studied over a wide intensity range and for various excitation wavelengths. The upconversion efficiency measured at room temperature varies linearly or quadratically with intensity and saturates at 100 W/cm2 or higher, depending on emission wavelength. For 4 mol % ErF3 in BaF2/ThF4, the 4I11/2 to 4I15/2 transition is over 10% efficient for 400 W/cm2 of absorbed 1.5-μm power, i.e., for 4I15/2 to 4I13/2 excitation. A rate equation model and Judd–Ofelt analysis of data for the glasses doped with just Er3+ provide an understanding of the upconversion process while yielding values for Er3+ energy-transfer rates and excited-state populations. These results could be used to develop glasses for lasing and as infrared optical detectors.

Devitrification of a heavy metal fluoride glass

The kinetic parameters of devitrification on reheating for the BIGaZYbTMn glass were determined using a differential scanning calorimeter. Isothermal and non-isothermal methods led to values of the Avrami's exponent between 1.5 and 2.5, corresponding to a diffusion controlled growth of crystals. The apparent activation energy E in all cases was close to 40 kcal/mol, very similar to ZBLAN glass, indicating an excellent stability of this glass to crystallization.

Process for making bulk heavy metal fluoride glasses: Joseph J Hutta assigned to The United States of America as represented by the Secretary of the Air Force

Process for making bulk heavy metal fluoride glasses: Joseph J Hutta assigned to The United States of America as represented by the Secretary of the Air Force

Fusion Splicing of Heavy Metal Fluoride Glass Optical Fibers

Fusion Splicing of Heavy Metal Fluoride Glass Optical Fibers

The Effect of Small Composition Changes on the Refractive Index and Material Dispersion in ZBLAN Heavy-Metal Fluoride Glass

The Effect of Small Composition Changes on the Refractive Index and Material Dispersion in ZBLAN Heavy-Metal Fluoride Glass