Study On L-band Rare Earth Garnet Growth And Liquid Phase Epitaxy Melt Formulation

Optical communication system is an important means of modern communication technology,and one of its basic components is optical isolator.The core material for realizing the non-reciprocity of the optical isolator is Faraday magneto-optical（MO）material,and the MO materials currently used in our country are all from the United States and Japan,which seriously endangers the security of China’s information field.Based on the above background,this thesis studies the core material of MO isolators for infrared L-band applications—rare earth substituted garnet（RIG）,starts with the melt formulation,finds the best melt formulation,and optimizes the process parameters.Realize practical thick film preparation.The experimental method for growing RIG in this thesis is liquid phase epitaxy（LPE）technology,which is based on the precipitation of RIG on a heterogeneous calcium-magnesium-zirconium-substituted garnet（SGGG）substrate in a supersaturated solution.So the chemical formula of supersaturated solution and the lattice matching of the RIG and the substrate are the two important points for the successful growth of the material.The specific composition of RIG is selected as（GdYbBi）₃Fe₅O₁₂ according to the application band.First,the proportion of each oxide in the melt is regulated.The experiment found that:in the Pb O-Bi2O3-B2O3 flux system,the（GdYbBi）₃Fe₅O₁₂ single crystal in the liquid phase epitaxial growth process with the increase of subcooling,the stress transition from tensile stress to compressive stress,and the content of Bi³⁺in the epitaxial film is also increasing;the viscosity change caused by the change of the flux system has the greatest influence on the growth process of（GdYbBi）₃Fe₅O₁₂ single crystal,and the increase of the B₂O₃ content will significantly reduce the saturation temperature and also have a significant limitation on the growth rate.Fe₂O₃ or rare earth oxides Gd₂O₃ and Yb₂O₃can effectively increase the growth temperature;the content of rare earth oxides Gd₂O₃ and Yb₂O₃ is positively correlated with the change of growth rate.Secondly,the crystal quality of（GdYbBi）₃Fe₅O₁₂ single crystal is mainly affected by the change from the flux system.When the molar ratio of each oxide in the solution has the following relationship,that is,when R₁≤25,R₃=2.5,R₆≥2.9,and R₇=55,the surface crystal quality of the grown epitaxial film is better.Finally,the（GdYbBi）₃Fe₅O₁₂ single crystal thick film was grown using the optimized growth parameters in this thesis.The obtained epitaxial film has a good mirror effect,and the specific Faraday rotation angle can reach 0.12 deg/μm at the wavelength of 1540 nm.The light absorption coefficient in the L-band is only 4 cm^-1,which indicates that the single-crystal film is a good material for the L-band.