The field of heavy metal halide glasses (namely fluorides) is only ten years old now, but it has developed rapidly since the discovery of fluorozirconate glasses by the group at the University of Rennes (France). The main reason for this was the early demonstration of the enormous potential of such glasses for use as long-haul ultra-low loss middle infrared waveguide materials, aided in part by the scientific interest held by their unusual short range structures. As a result, significant research efforts were initiated in the academic, government and industrial sectors in Europe, the United States and Japan. However, the search for a finished product has per­ haps led to a partial overlooking of some of the more funda­ mental aspects by the scientific community. After the initial excitement, the workers in this field are perhaps at a crossroads where attenuations lower than 1 dB/Km need to be obtained for long lengths of fiber of good chemical and thermal stability, in order to guarantee continual R&D sUE ports. Therefore, there is a strong need for a critical asses­ sment of the potential of halide glasses for infrared fiber­ optics and the formulation of recommendations for future re­ search in this area and other related fields.

Inhalt

I. History.- The First Ten Years.- II. Raw Materials and Purity.- High Purity Components for Fluorozirconate Glass Optical Fibers.- Chemical Analysis of Trace Impurities.- Role of Impurities in Halide Glasses.- III. Structure.- Vibrational Spectroscopy Studies of Halide Glass Structure.- Diffraction Studies of Halide Glasses.- Molecular Dynamics Simulations of Fluorozirconate Glass Structure.- IV. Thermal and Mechanical Behavior.- Viscosity Behavior of Halide Glasses and Melts.- The Thermal Properties of Fluoride Glass.- Structural Relaxation in Fluoride Glasses.- Crystallization Behavior of Fluorozirconate Glasses.- Physical, Chemical Properties and Crystallization Tendency of the New Fluoroaluminate glasses.- Surface Chemistry and Slow-Crack Growth Behavior of Fluorozirconate glasses.- V. Optical Properties of Glasses and Fibers.- Optical Properties of Fluoride Glasses.- Optical Properties of Rare-Earth and Transition Metal Ions in Fluoride glasses.- Loss Mechanisms in ZrF4 Based IR Fibres.- VI. Fiber Fabrication.- Fluoride Glass Optical Fibers in France.- Progress in Fiber Preparation in Japan.- Vapor Deposition of Fluoride Glasses.- VII. Fiber Systems.- Waveguide Systems Development.- Applications of Infrared Waveguides in Remote Gas-Spectroscopy.- VIII. Other Vitreous Halides.- Zirconium-Free Fluoride Glasses.- Chemical Durability of a BaF2-ThF4 Based Glass.- Transition Metal Fluoride Glasses (TMFG), Synthesis, Properties, Structure.- Chloride, Bromide and Iodide Glasses.- IX. Related Fields.- Halide Glasses and Chalcogenide Glasses for Ultra Low Loss Fibre Applications - a Comparison.- Interactions with Other Fields.- Short Communications.- Glass Formation in Halide Systems.- Preparation of Fluoronitride Glasses.- PL measurements on fluorozirconate glasses.- Concluding Remarks.- List of Participants.