Chemical stability of chalcogenide infrared glass fibers

Infrared fibers from the chalcogenide family are becoming increasingly prevalent for applications in optical sensing and imaging. In this work, we study the chemical stability of these fibers during long-term storage in air and medium term immersion in water comparable to normal usage conditions during optical monitoring in aqueous environments. A detailed study of surface oxidation in Te-As-Se fibers shows that the oxidation is limited to a superficial layer and progress at a rate of about 20 A per year. While the elemental glass is insoluble in water, the oxide layer solubilizes rapidly and can lead to surface pitting after oxide removal. The dissolution process is complete after about 2 h of immersion in water. The elemental glass on the other end is chemically stable in water and no significant oxidation process can be detected by cyclic voltammetry. Finally the useful optical properties of these fibers are essentially unchanged after extended storage or immersion in water despite surface oxide or surface pitting.