A. David Pearson

FILAMENTARY CONDUCTION IN SEMICONDUCTING GLASS DIODES

Electrical switching in thin‐film As2SeTe2 semiconducting glass diodes with thin‐film electrodes has been studied. The formation of a liquid phase and what appear to be conducting filaments have been observed and recorded. Current densities > 104 A cm−2 have been estimated in the filaments.

PREPARATION OF A LIGHT FOCUSING GLASS ROD BY ION‐EXCHANGE TECHNIQUES

A glass rod with a radially graduated refractive index was produced by replacing the lithium ions contained in the glass composition with sodium ions from a fused salt bath. Glass rods with such refractive index gradients are potentially useful as low resolution imaging devices.

Low‐loss fused silica optical waveguide with borosilicate cladding

Optical waveguides consisting of a pure fused silica core and borosilicate cladding were produced by using chemical vapor deposition techniques. A typical guide showed an optical attenuation of 7.5 ± 1.5 dB/km, measured at 0.63 μm (He–Ne laser). In one of the guides whose loss spectrum was studied, the attenuation was less than 20 dB/km between 0.55 and 0.86 μm except for the third OH overtone at ∼ 0.72 μm. The lowest loss of this waveguide occurred at 0.80 μm, with other minima at 0.66 and 1.06 μm.

Loss Mechanisms and Measurements in Clad Glass Fibers and Bulk Glass

Optical-loss mechanisms and transmission losses were investigated in clad glass fibers and in the bulk glass from which they were drawn. Measurements of the total losses, absorption losses, and scattering losses in both the fibers and in the bulk materials are presented and compared. Photomicrographs of scattered light were made at 90° with 0.6328-μm laser light propagating in the fiber core. These revealed the presence of an extremely large number of discrete light-scattering centers, both in the core and in the cladding. Similar photomicrographs of the bulk materials also show the presence of discrete scattering centers. Scattering centers have also been observed by means of an electron microscope; they have been shown to be crystalline, by both electron diffraction and x-ray diffraction.

Memory and switching in semiconducting glasses: A review

Abstract Semiconducting glass diodes can exhibit several conducting states. A high resistance, or off state; a low resistance, or on state; a negative resistance state; and a memory on state have been reported. The data published on the laboratory operation of simple diodes and the methods of inducing transitions between the various states are reviewed. In addition, various suggestions which have been made to explain the mechanism of device operation are discussed.

The mechanism of hologram formation in arsenic-sulfur glass

Abstract Glass of composition 7 mole % As, 93 mole % S was examined using calorimetry, chemical extraction and electron spin resonance in order to determine the mechanism whereby phase holograms are formed in this material. We have determined that, after hologram formation, the material consists of a glassy matrix with microcrystals of almost pure α sulfur. The same process (precipitation of α microcrystals) can be induced thermally in these glasses, but the photo-induced change is markedly faster.

Determination of the absorptivity of OH in a sodium borosilicate glass

The absorptivity of OH in a sodium borosilicate glass has been determined. The method consisted of measuring the weight loss and the decrease in absorbance at 2825 nm after heat-treatment of polished slices of glass in a dry nitrogen atmosphere. The confusion in the literature involving “water” content and OH content of glasses is also discussed.

Laser Oscillations at 0.918, 1.057, and 1.401 Microns in Nd3+‐Doped Borate Glasses

Borate glasses doped with Nd3+ have been prepared in small (70 g) batches, and rods of sufficiently high optical quality for laser oscillations have been pulled directly from the melts. Laser action occurs in three groups of wavelengths, the strongest emission being at 0.918, 1.057, and 1.401 μ. Plots of the threshold for oscillation at 1.057 μ are given as a function of both Nd2O3 concentration and base glass composition.

Energy Exchange from Nd3+ to Yb3+ in Calibo Glass

Studies of energy exchange from Nd to Yb in calibo glass were made using the technique of time‐resolved spectroscopy. The rate of energy exchange between the systems was of the order of 3×104/sec, while the quantum efficiency for the process was estimated at 0.6. The mechanism is predominately nonradiative.

Ion beam polishing of glass

Abstract Samples of glass, “scratched” with Linde A alumina (0.3μ) were bombarded with argon ions at high angles of incidence. Using a sample holder which allowed sample rotation during bombardment, the scratches were removed. In addition, in some cases, microstructure in the glass was revealed.