Low-Hydroxyl tellurite fiber for Mid-Infrared Er:YAG laser transmission

Due to pronounced hydroxyl (–OH) absorption bands around 2.7 μm in the mid-infrared region, tellurite glasses typically exhibit limited performance for mid-infrared laser transmission, which in turn constrains their suitability for Er:YAG laser delivery. This limitation arises primarily from –OH impurities, which introduce strong absorption in the mid-infrared band and significantly degrade transmission efficiency. To enhance the mid-infrared transmission performance and laser-induced damage threshold of TeO 2 –ZnO–La 2 O 3 (TZL) glass, high-temperature vacuum melting was employed as a physical purification method to effectively remove –OH impurities from the glass matrix. The effects of melting temperature and vacuum level on purification efficiency were systematically investigated. Through optimization of raw-material refining and melting parameters, low-hydroxyl tellurite glass was successfully obtained, exhibiting an –OH absorption coefficient as low as 0.004 cm –1 —representing a 99.8% reduction compared with conventional unpurified samples. The purified glass was subsequently extruded into core–cladding preforms and drawn into flexible fibers with a core diameter of 300 μm and a cladding diameter of 600 μm. The fabricated TZL fiber achieved a maximum stable output power of 8.3 W at 2.94 μm, corresponding to an energy density of 1061 J cm –2 . To the best of our knowledge, this is the first demonstration of a tellurite fiber capable of stably delivering more than 8 W of Er:YAG laser power at 2.94 μm, highlighting its strong potential for high-power mid-infrared laser applications in surgical medicine and industrial processing.