Effect of aluminum and tellurium tetrachloride addition on the loss of arsenic selenide optical fiber

Abstract Arsenic selenide glass optical fibers typically possess extrinsic absorption bands in the infrared wavelength regions associated with residual hydrogen and oxygen related impurities, despite using 6N purified elemental precursors. Consequently, special additives and refined processing steps are utilized in an attempt to reduce these and other impurities. We investigate the formation of particulate impurities during a purification process based on the addition of 0.1 wt% elemental aluminum (Al) and 0.2 wt% tellurium tetrachloride (TeCl 4 ) during glass synthesis. It was found that during purification and melting steps, Al reacts with TeCl 4 to form AlCl 3 , which in turn reacts with oxygen and hydrogen impurities and the fused quartz (SiO 2 ) ampoule to produce HCl and stable submicron Al 2 SiO 5 compounds in the As-Se glass and fibers. The intensity of the H-Se absorption band centered at 4.57 μm has been significantly reduced from 18 dB/m to 0.8 dB/m. Using thermodynamic data, we have identified stable Al 2 SiO 5 submicron inclusions in the glass and fibers. A two-step gettering process is proposed as a solution to eliminating these inclusions.