Gallium lanthanum sulphide fiber for active and passive applications

Abstract

Optical fibres drawn from sulphide-based glasses have been studied now for almost two decades. Initial work began in the 1970s when fibres from glasses based on arsenic sulphide or germanium sulphide rapidly found application as infrared waveguides, providing transmission to beyond 5 microns. 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 widespread activity with the goal of demonstrating a low-loss sulphide glass optical fibre and an 1300 nm optical fibre amplifier. Today, research on several families of sulphide glass, including gallium lanthanum sulphides, germanium sulphides and halide-modified glasses has progressed to the point where several of these materials have been drawn into fibre form. However, application of fibre is critically dependent on the achievement of a low loss single-mode optical fibre which has yet to be achieved. At Southampton, our work has focussed on gallium lanthanum glass and fibre, for both active and passive applications. As part of our ongoing programme, optical, thermal and mechanical properties of these glasses are under study. In parallel with this, fibre drawing is being refined in a quest for practical fibres. Over the past year, improvements have been made in understanding and eliminating the sources of loss in these glasses. In this paper, we describe the current specifications of fibres based on this material group. Recent progress in several applications, in particular those extending into the infrared will be reported and the prospects for a future generation of sulphide-fibre based devices examined.