Heavy metal fluoride glass fibers and their applications

The availability of high quality optical fibers with transmission window, larger than that of silica fiber, extends the use of optical fibers and open new application fields. There is increasing demand of optical fiber with transmission over 2 microns, where silica is opaque, for applications as diverse as sensing, fiber lasers and amplifiers, defense (IRCM), spectroscopy... No materials can fulfill all applications needs. Engineers have to make some compromise when choosing the right materials for the right application. Heavy metal fluoride glass is one of these materials. The glass, under bulk form, has a wide transmission window from 0.3 up to 8 microns, without any absorption peaks. Heavy metal fluoride glass fibers are drawn using the preform technique, the same technique used for silica fiber. This technique has proven to allow good control of fiber dimensions and geometry. Fluoride glass fibers with different exotics shapes have already been obtained, such as D-shaped, square, of centered fiber, multi cladding fibers and microstructured fibers.... As far as active fibers are concerned, heavy metal fluoride glasses have low phonon energy and can contain high concentration of active ions, rare-earth elements. Therefore, new laser lines have been already demonstrated using fluoride glass fibers. Fiber lasers with output power exceeding 10 w have been obtained by different groups. This paper will present the latest development of fluoride glass fiber technology, including fibers optical and mechanical properties, fiber lasers and power handling.