Stimulated Brillouin scattering (SBS) and thermal management limit the increase of the ultimate output power of glass fibers in fiber lasers. Yttrium aluminum garnet (YAG) crystal fiber combines the advantages of crystal and fiber. Compared with glass fiber, its SBS gain coefficient is lower, Which can effectively reduce nonlinear effects and thermal damage, and provide a new direction for fiber laser research. After the YAG crystal reaches the melting point (1 970 ℃), it will quickly melt into a low-viscosity liquid, which is not conducive to the preparation of crystal fiber. Preparation of YAG crystal core/glass cladding composite fiber is the main method to study YAG crystal fiber, but there are problems of vitrification of YAG crystal core, component diffusion between core and cladding, and excessive numerical aperture. It is difficult to grow undoped YAG crystal as the cladding layer of the rare-earth-doped YAG crystal core, and further research is needed. At present, the YAG crystal fiber is prepared by laser heating pedestal growth technology (LHPG) and micro pull-down method (μ-PD), and the quality of the prepared fiber is better. The research on YAG optical fiber focuses on using glass or crystal with matching refractive index and thermal expansion as YAG crystal as the cladding, and exploring the composite process to reduce the numerical aperture and reduce the diffusion between the core and the cladding. The maximum output power reported in the existing paper is 590 W. This article introduces several preparation methods of YAG crystal fiber, and status of the unclad rare earth doped YAG crystal fiber, glass cladding rare earth doped YAG crystal composite fiber, YAG crystal cladding crystal fiber and fusion of YAG crystal fiber and traditional passive fiber device is reviewed, The current research status is summarized and forecasted. © 2021, Materials Review Magazine. All right reserved.
