Long‐Wave Infrared‐Transmitting Optical Fibers

Tellurium‐enriched high‐purity chalcogenide fibers were fabricated and their infrared (IR)‐transmitting properties were investigated. The thermal stability of Ge–As–Te glasses could be improved significantly by introducing a small amount of selenium into the glasses, therefore allowing the production of structurally and optically homogeneous glass fibers with minimal scattering losses. The fibers with greater electrical conductivity (σ) showed higher transmission losses than those with smaller σ because of the severer free‐carrier absorption in the former, which was identified by the temperature dependence of the fibers' attenuation. In an effort to reduce σ of the glass while maintaining its outstanding transmitting property in the long‐wave IR region, iodine was added to replace a quantity of tellurium in the glass. The fiber made of Ge 25 Te 58 I 7 Se 10 glass exhibited good transmitting property in the 4–12 μm region and showed losses as low as ∼1 dB/m around 9.5 μm.