Magnesium-Ion Indiffusion to Lithium Niobatc Single-Crystal Fiber with MgFa as Diffusion Source

A study of the Mg-ion indiffusion to lithium niobatc (LiNbO₃) single-crystal fiber was carried out using MgF₂ as the diffusion source. A core-cladding waveguide structure was obtained for a c-axis LiNbO₃ single-crystal fiber with a diameter of 200 μm, and the optical characteristics of the cladded crystal fiber were given. By means of electron probe microanalysis, the activation energy for Mg-ion indiffusion was estimated to be 104kJ/mol. It was also found by X-ray diffraction analysis that the Mg-diffused layer has serious lattice distortion and the LiNb₃O₈ compound appears beyond a certain extent of Mg-ion indiffusion. The appearance of the LiNb₃O₈ compound is related to Li-ion outdiffusion from the bulk of LiNbO₃ and the large amount of F ions from MgF₂ due to Mg-ion indiffusion to LiNbO₃. It was indicated by scanning electron microscopy that F ions appear in the form of LiF particles and these particles volatilize from the surface of the Mg-diffused layer with increased diffusion.