Fluoride glasses: synthesis and properties

Abstract

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 .