Processing and transparency of polycrystalline yttrium aluminum garnet (YAG) fibers for optical applications

Polycrystalline YAG fibers are of interest for both optical and structural applications. Various processing routes of YAG fibers for structural applications have been explored; however, processing routes for optical quality polycrystalline YAG fiber have not been investigated intensively despite the potential of the material to enable high power lasers. Recent results in the processing of YAG fiber for laser applications are presented and detailed relationship between processes, microstructures, and optical properties of YAG fibers are discussed. Specifically, details of the processes for green fiber preparation, sintering methods, and transparencies depending on the process variables are shown. Our recent advancement in fiber processing prior to sintering has improved the transparency of YAG fiber significantly. Vacuum or air sintering followed by Hot Isostatic Press (HIP) produced fibers with transparency comparable to that of single crystal YAG fiber.