Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Exper...Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Experimental results indicate that, after an annealing at 950 degreesC for 14 h under low As pressure, the Hall mobility decreases and the resistivity increases dramatically for the samples. These changes in electrical properties are due to the generation of intrinsic acceptor defects, and the generation of the intrinsic acceptor defects originates from the outdiffusion of As interstitial at high temperature. The generation of the intrinsic defects and these changes in electrical properties can be suppressed by increasing the applied As pressure during annealing. The concentration of the main donor defect E12 (AsGaVGa) can be decreased by about one order of magnitude by an evacuated annealing at 1120 degreesC for 2-8 h followed by a fast cooling. The decrease in E12 concentration can also be suppressed by increasing the As pressure during annealing.展开更多
An iterative procedure is proposed for the variational analysis of Ti:LiNbO3 optical waveguides. A trial solution for the dominant electric field profile of arbitrary-order eigenmodes in strip waveguides and two coupl...An iterative procedure is proposed for the variational analysis of Ti:LiNbO3 optical waveguides. A trial solution for the dominant electric field profile of arbitrary-order eigenmodes in strip waveguides and two coupled waveguides is proposed and its parameters are determined using the variational method. The results calculated using this method agree well with those obtained using the finite-element method. The present method has been used to check the accuracy of the effective index method as well as a quasi-analytical technique based on the effective index method. The results show that the effective index method is generally accurate for the fundamental mode and becomes less accurate for higher-order vertical modes.展开更多
A core-cladding waveguide structure of lithium niobate single crystal fiber with different refractive index profiles has been obtained by using an Mg-ion indiffusion process. The propagation loss of the dadded crystal...A core-cladding waveguide structure of lithium niobate single crystal fiber with different refractive index profiles has been obtained by using an Mg-ion indiffusion process. The propagation loss of the dadded crystal fiber is measured to be 14 times as low as that of the undadded crystal fibers. Mechanisms of Mg-ion indiffusion and reasons of lattice distortion are analyzed and discussed. It is found by X-ray diffraction analysis as well as scanning electron microscopy that MgO-rich layer in the magnesium diffused surface exhibits the crystal structure of a new compound from the Li-Mg-Nb-O ternary system. It is proposed, for the first time, that this new compound in MgO-rich layer is the real source of Mg-ion indiffusion lithium niobate.展开更多
文摘Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Experimental results indicate that, after an annealing at 950 degreesC for 14 h under low As pressure, the Hall mobility decreases and the resistivity increases dramatically for the samples. These changes in electrical properties are due to the generation of intrinsic acceptor defects, and the generation of the intrinsic acceptor defects originates from the outdiffusion of As interstitial at high temperature. The generation of the intrinsic defects and these changes in electrical properties can be suppressed by increasing the applied As pressure during annealing. The concentration of the main donor defect E12 (AsGaVGa) can be decreased by about one order of magnitude by an evacuated annealing at 1120 degreesC for 2-8 h followed by a fast cooling. The decrease in E12 concentration can also be suppressed by increasing the As pressure during annealing.
基金Project supported in part by the National Natural Science Foundation of China,Science Foundation of Guangdong Province,Zhongshan University,Chinese Post-doctoral Committee.
文摘An iterative procedure is proposed for the variational analysis of Ti:LiNbO3 optical waveguides. A trial solution for the dominant electric field profile of arbitrary-order eigenmodes in strip waveguides and two coupled waveguides is proposed and its parameters are determined using the variational method. The results calculated using this method agree well with those obtained using the finite-element method. The present method has been used to check the accuracy of the effective index method as well as a quasi-analytical technique based on the effective index method. The results show that the effective index method is generally accurate for the fundamental mode and becomes less accurate for higher-order vertical modes.
基金the Fund of Electronic Materials Research Laboratory, Xi'an Jiaotong University
文摘A core-cladding waveguide structure of lithium niobate single crystal fiber with different refractive index profiles has been obtained by using an Mg-ion indiffusion process. The propagation loss of the dadded crystal fiber is measured to be 14 times as low as that of the undadded crystal fibers. Mechanisms of Mg-ion indiffusion and reasons of lattice distortion are analyzed and discussed. It is found by X-ray diffraction analysis as well as scanning electron microscopy that MgO-rich layer in the magnesium diffused surface exhibits the crystal structure of a new compound from the Li-Mg-Nb-O ternary system. It is proposed, for the first time, that this new compound in MgO-rich layer is the real source of Mg-ion indiffusion lithium niobate.
