Yb₂O₃-doped YAG nano-crystallites in silica-based core glass matrix of optical fiber preform

Yb2O3-doped yttrium aluminium garnet (YAG) nano-crystals within the silicate glass-based optical fiber preforms were obtained through the conventional-modified chemical vapour deposition (MCVD) and solution doping technique. Nano-crystals were developed with soaking of the porous phospho-silica or pure silica core layer in a solution containing the ytterbium, yttrium and other co-dopants, including fluorine using 10-15% fluorosilicic acid, and through post-annealing of the preform at a temperature of around 1450 °C. The size, shape and nature of Yb2O3-doped phase-separated nano-crystallites were evaluated from HRTEM images along with the electron diffraction pattern based on the doping levels of phosphorous and fluorine. The size of nano-crystallites was maintained within 6-10 nm when doped with 0.25 mole% of fluorine. X-ray analyses EDX data reveals that the nano-particles are rich in Yb:YAG, and uniformly dispersed into the amorphous silica glass matrix. The novelty of this technique involves the direct synthesis of rare-earth doped phase-separated nano-crystallites within the core region of silica glass preforms. This class of fibers containing the nano-particles with or without Yb:YAG crystalline nature will keep the advantage of the mechanical properties as well as good lasing properties under high power application compared to the Yb:YAG ceramic laser