A three-color, solid-state, volumetric display based on two-step, two-frequency upconversion in rare earth-doped heavy metal fluoride glass is described. The device uses infrared laser beams that intersect inside a transparent volume of active optical material to address red, green, and blue voxels by sequential two-step resonant absorption. Three-dimensional wire-frame images, surface areas, and solids are drawn by scanning the point of intersection of the lasers around inside of the material. The prototype device is driven with laser diodes, uses conventional focusing optics and mechanical scanners, and is bright enough to be seen in ambient room lighting conditions. QuickTime movie of the three-dimensional display.

https://science.sciencemag.org/content/sci/273/5279/1185.full.pdf

A Three-Color, Solid-State, Three-Dimensional Display

Chemical processes which occur during glass polishing are reviewed within the context of current mechanical models for the polishing process. The central chemical process which occurs is the interaction of both the glass surface and the polishing particle with water. A detailed mechanico-chemical model for the polishing process is proposed.

Chemical processes in glass polishing

The new crystalline material family, lithium superionic conductor (thio-LISICON), was found in the Li 2 S-GeS 2 -P 2 S 5 system. The solid solution member x x 0.75 in Li 4-x Ge 1-x P x S 4 shows the highest conductivity of 2.2 x 10 -3 S cm -1 at 25°C of any sintered ceramic together with negligible electronic conductivity, high electrochemical stability, no reaction with lithium metal, and no phase transition up to 500°C. Its material design concepts of changing constituent ions with various ionic radii, valence, and polarizability are described.

https://iopscience.iop.org/article/10.1149/1.1379028/pdf

Lithium Ionic Conductor Thio-LISICON: The Li2 S ­ GeS2 ­ P 2 S 5 System

Infrared and near-infrared transmission spectra have been taken on 19 volcanic and synthetic silicate glasses with known H2O contents (0.06–6.9 wt. %). Absorption peaks were observed at wavelengths of 1.41 μm, 1.91 μm, 2.22 μm, 2.53 μm, and 2.8 μm. These peaks have been attributed to the first overtone of the OH stretching vibration, the combination stretching+bending mode of H2O molecules, the combination stretching+bending mode of X-OH groups, a combination mode of the fundamental OH stretch+a low energy lattice vibration, and the fundamental OH stretching mode, respectively. Molar absorptivities of the peaks have been determined to be 0.2, 1.8, 1.0, 0.9, and 67 l/mol-cm. These values apply over the full range of glass compositions studied (albite, rhyolite, basalt).

Water in silicate glasses: An infrared spectroscopic study

The mixed alkali effect in glass refers to the large, orders of magnitude, changes in many properties when a second alkali oxide is added. Properties most affected are those associated with alkali ion movement such as electrical conductivity and loss, alkali diffusion, internal friction, viscosity and chemical durability. The compositional dependence of these properties is briefly reviewed and examples are given of the relevance of the mixed alkali effect to the manufacture of commercial glasses. Also reviewed are various theories for this scientifically interesting effect.

Mixed alkali glasses — Their properties and uses

Infrared absorption was measured on an NajO-K2O-ZnO-Al2O3-SiO2 glass with up to ∼11 wt% water. Fundamental and overtone-combination bands were observed at 1.41, 1.91, 2.22, 2.87, and 6.1 μm. Molar absorptivities were determined for the hydrated glass for H2O and OH levels using the molar absorptivity calculated for the 2.22-μm band in the as-melted glass. By this procedure the concentration of molecular water and OH groups could be determined separately. These results show that the OH content of the hydrated glass, as determined from the 2.22-μm band, is constant at >7 wt% H2O; additional H2O is attributed to molecular water only. Good agreement was found between these data and H2O/OH molecular ratios obtained from NMR.

Infrared Spectra of a Water‐Containing Glass

The infrared and visible spectra of glasses in the Ag2OP2O5 glass-forming system were obtained. The infrared data were interpreted as indicating the presence of polymeric chains in these glasses. The partial covalent nature of the AgOP bond was discussed. A mixed NaPO3AgPO3 glass showed no unexpected bands in the infrared spectrum, again showing that silver is behaving in a manner similar to alkali metal ions in phosphate glasses. The shift in the absorption edge in the visible spectra of glasses of different Ag/P ratio was shown to arise from either an increase in the concentration of nonbridging oxygens with increasing silver content, or the presence of colloidal silver metal particles.

Structure and properties of silver phosphate glasses — Infrared and visible spectra

A package for a high power semiconductor laser comprising a hermetically sealed container filled with a dry gaseous medium containing oxygen. The presence of oxygen in the laser atmosphere is counter to standard practice in the art which teaches the use of an atmosphere of a dry inert gas. The package also includes a getter for organic impurities, e.g., a getter composed of a porous silica or a zeolite. The hydrogen content of the materials used to form the package are reduced by baking at an elevated temperature for an extended period of time, e.g., at 150° C. for 200 hours.

Packaging of High Power Semiconductor Lasers

A wide-line NMR study is reported of glasses containing from 3.6 to 41 wt % H 2 O. Proton wide-line NMR spectra at low temperatures show that the protons are present as hydroxyl groups and water. As the temperature is increased, the line width decreases, evidence for the increased mobility of the water molecules. The hydroxyl content appears to be relatively low, almost independent of the total proton content. Na 23 spectra in a glass containing 32.5 wt % water were studied. At 100°C the Na + ions were found to be very mobile. It is shown that when the glass network is ruptured a limited number of hydroxyl groups is formed. However, most of the water is present in the opened-up glass structure as molecular water.

Wide-line NMR study of protons in hydrosilicate glasses of different water content

The synthesis of glasses with water contents greater than a few tenths of a weight percent water necessitates the temperatures and pressures attainable in an autoclave. Compositions that readily hydrate contain both alkali metal oxide and silica. Examples will be presented of different composition fields. Parameters affecting the kinetics and techniques to control final water contents will be described. Structural information obtained from infrared spectra show that both hydroxyl and molecular water groups are present. Properties of the glass can be drastically altered. Physical, mechanical and chemical properties will be discussed.

Roger F. Bartholomew

Papers

Infrared Spectra of a Water‐Containing Glass

Structure and properties of silver phosphate glasses — Infrared and visible spectra

Packaging of High Power Semiconductor Lasers

Wide-line NMR study of protons in hydrosilicate glasses of different water content

High-water containing glasses