Fabrication of Arsenic Sulfide Optical Fiber with Low Hydrogen Impurities

Arsenic sulfide glass optical fibers typically possess extrinsic absorption bands in the infrared wavelength region associated with residual hydrogen and oxygen related impurities, despite using purified precursors. We report a purification process based on the addition of tellurium tetrachloride (TeCl₄) to the glass. During melting, the chlorine from TeCl₄ reacts with the hydrogen impurities to produce volatile products (e.g., HCl) that can be removed by subsequent dynamic distillation. The processing conditions have been modified accordingly to produce optical fibers with significantly reduced loss due to hydrogen sulfide impurity content (1.5 dB/m).     

Transparent ceramics for high-energy laser systems

We demonstrate that transparent magnesium aluminate spinel ceramic possesses excellent thermo-optical properties, a record low absorption loss of 6 ppm/cm, and superior ruggedness which position it as a prime candidate for an exit window aperture for high energy laser systems, especially in hostile environments. We also demonstrate lasing with an efficiency of about 45% in transparent Yb³⁺:Y₂O₃ ceramic made by hot pressing high purity submicron co-precipitated powder. This paves the way forward for high power solid state lasers exploiting hosts with higher thermal conductivity than YAG.     

Fuelwood and stoves: Lessons from Zimbabwe

Laboratory tests on traditional open fires as methods of cooking give values of thermal efficiency varying from 12–30%. These are significantly higher than values which are widely quoted in the literature. The results of a research visit to Zimbabwe indicated that in three villages fuel efficiency did not appear to be the main determinant of choice of cooking method: villagers had changed from their traditional mode of cooking to stoves which they perceived to consume substantially more fuel. These stoves enabled meals to be prepared more quickly which the women found useful during the busy months. The increased labour costs could be borne because fuel was gathered during the slack season.     

Financing energy efficiency in developing countries—lessons learned and remaining challenges

Although energy efficiency implementation is increasingly being recognized by policymakers worldwide as one of the most effective means to mitigating rising energy prices, tackling potential environmental risks, and enhancing energy security, mainstreaming its financing in developing country markets continues to be a challenge. Experience shows that converting cost-effective energy savings potential, particularly the demand-side improvement opportunities across sectors, into investments face many barriers and unforeseen transaction costs. This paper draws upon selected experiences with financing energy efficiency in developing countries to explore the key factors of various programmatic approaches and financing instruments that have been applied successfully for delivering energy efficiency solutions. Through case studies, a diverse range of institutional issues are examined related to the identification, packaging, designing, and monitoring approaches that have been used to catalyze traditional and innovative financing of energy efficiency projects. With adequate liquidity in major developing country markets and availability of modern energy savings technologies, it is often the institutional issues that become a key challenge to address in order to finance and implement robust programs. As further operational experience is gained, increased knowledge sharing can lead to scaling-up of such energy efficiency investments. The paper concludes with some ideas for accelerating implementation.     

Micro-Raman Analysis of Carbon Inclusions in Heavy-Metal Fluoride Glasses

While vitreous carbon crucibles can be used to produce high-quality heavy-metal fluoride glasses using low concentrations of SF₆ gas (15%), pure SF₆ gas produces low-quality and high-scattering glasses. This has been attributed to contamination by vitreous carbon particles by a fallback mechanism due to reaction of SF₆ gas with the crucible walls above the melt. The detrimental effect of carbon particles is further highlighted by their high scattering efficiency factor which indicates that only 37 particles of 1-μm diameter can be tolerated in an optical fiber for attaining 0.01 dB/km loss.     

Properties of As40S(60–x) Sex Glasses for IR Fiber Optics

The physical and optical properties of glasses in the As₄₀S₍₍₆₀-_x:)Se_x system where x = 0, 5,10,15, and 20 at. % Se have been investigated. The changes in the glass transition temperature, density, hardness, IR edge, and refractive index can be attributed to the presence of Se, which simply replaces S in these glasses. The glasses do not exhibit crystallization under the conditions used in this study, which is a desirable property from the viewpoint of flberization. Appropriate core and cladding glass compositions have been identified for fabrication of optical fibers with known numerical apertures. Furthermore, it has been shown that these glasses will not impart additional thermal or mechanical stresses in optical fibers made from these compositions.     

Low Cost Concurrent Error Detection Strategy for the Control Logic of High Performance Microprocessors and Its Application to the Instruction Decoder

We propose a low cost concurrent error detection strategy to improve the Reliability, Availability, Serviceability (RAS) of high performance microprocessors, by specifically targeting one of its most critical blocks (from the point of view of the microprocessor RAS), that is the control logic. By discovering codes that are inherently present within the control logic because of its performed functionality and verification needs (referred to as Control Logic Function-Inherent Codes), it allows to achieve concurrent error detection at very limited costs in terms of area, power consumption, impact on performance and design. Considering for instance the case of the instruction decoder of a public domain microprocessor, we will prove that our approach requires significantly lower area and power than traditional parity encoding, while providing higher concurrent error detection ability. Therefore, if adopted together with a system level (generally software implemented) recovery technique, our strategy constitutes a viable and successful approach to increase the microprocessor RAS, at very limited costs.