Application of novel chalcogenide glasses based on gallium and lanthanum sulphides in optical fibre devices

Optical fibres drawn from sulphide-based glasses have been studied now for almost two decades. Initial work began in the 1970s where fibres from glasses based on arsenic sulphide or germanium sulphide rapidly found application as infrared waveguides, providing transmission to beyond 5 microns. In the early 1990s, the demonstration of an optical fibre amplifier for the 1300 nm telecommunications window, motivated again the application of non-silica optical fibres. First, a fluoride fibre device showed amplification with pump efficiencies of only a few percent. In 1993, the first active application of a sulphide glass was demonstrated and measurements on bulk samples of rare-earth doped gallium lanthanum glass showed the possibility of pump efficiencies of over 60%. This lead to a widespread activity to demonstrate a low-loss sulphide glass optical fibre and an 1300 nm optical fibre amplifier. Since that time, research into gallium lanthanum glass and fibre has expanded into several new areas. In this paper, research work at the ORC on sulphide fibres for active applications will be described. Recent progress, including the 1.3 micron amplifier, photonic switching and work extending into the infrared will be reported. Our work is critically depend on the achievement of a low loss single-mode optical fibre. Over the past year, significant improvements have been made in understanding and eliminating the sources of loss in these glasses. The current status of fibre drawing work will be outlined and, together with our spectroscopy and device work, the prospects for a future generation of sulphide-fibre based devices examined.