Development and evaluation of optical-use MgO : LiNbO_3 single crystals by line-focus-beam acoustic microscopy

线聚焦光束（LFB）声学显微镜是一种非常有用和独特的材料定量表征方法，它通过V (z)曲线分析来测量在试样与水耦合边界上激发的泄漏表面声波（LSAWs）的速度，具有良好的方向性。该系统已应用于MgO深度LiNbO_3晶体的科学和工业领域的材料问题，用于建立晶体生长条件和评价器件制造工艺。建立了可靠的LFB系统，在100 mm X 100 mm的整个扫描区域内，LSAW速度精度优于0.01%。6个掺杂MgO的LiNbO_3晶体，在不同的MgO掺杂浓度（0 ~ 13mol %）下生长，用于速度测量。首次证明了随着掺杂浓度的增加，X、Y、z切割面三个基本晶面上的速度均呈单调增加趋势，并且随着掺杂浓度的增加，各传播方向的速度均呈单调减少趋势。测量的LSAW速度与测量的化学和物理性质，即化学成分、密度、晶格常数、折射率和居里温度进行了比较。结果表明，LFB系统在测定这些性质方面比任何其他分析方法具有更高的灵敏度和分辨率。对直径为3英寸、长为80毫米的MgO (5mol %): LiNbO_3单晶基片进行了LSAW速度分布的测量。成功地获得了最大差异约3m/s的LSAW速度分布，这可能反映了熔体化学成分、旋转和拉拔速度等晶体生长条件的变化，以及坩埚和炉内的温度分布。该系统已用于表征层厚为0.5 μ m的Z-cut MgO (5mol%): LiNbO_3衬底上的质子交换层。结果表明，该系统能够分辨2 nm的扩散深度变化和5 × 10^<-4>的异常折射率变化。该方法应作为一种新的分析技术，用于开发和评估未来大规模生产的波导型光学器件制造工艺和系统。少

Line-focus-beam (LFB) acoustic microscopy, with perfect directionality, is a very useful and unique method of quantitative material characterization by measuring the velocity of leaky surface acoustic waves (LSAWs), excited on the boundary between the specimen and the water coupling, through V (z) curve analysis. The system has been applied to material problems in the scientific and industrial fields of MgO deped LiNbO_3 crystals for estabishment of the crystal growh conditions and for evaluation of the device fabrication processes.1.The reliable LFB system with high accuracy in LSAW velocity of better than 0.01% over an entire scanning area of 100 mm X 100 mm has been established.2.Six MgO-doped LiNbO_3 crystals, specially grown with different MgO dopant concentrations ranging from 0 to 13 mol%, have been employed for velocity measurements. It has been shown for the first time that the velocities on the three basic crystal surfaces of X-, Y-, and Z-cut planes increase for all the surf … More aces and all the propagation directions monotonically as the dopant concentration increases, and the corresponding density decrease monotonically.3.The measured LSAW velocities have been compared with the measured chemical and physical properties, viz., chemical composition, density, lattice constant, refractive index, and Curie temperature. It has been shown that the LFB system has a much greater sensitivity and resolution in the determination of these properties than any other analytical methods.4.Measurements of LSAW velocity distribution have been carried out for substrates obtained from a MgO (5 mol%) : LiNbO_3 single crystal with 3-inch diameter and 80 mm long. LSAW velocity distributions with the largest difference of about 3m/s have been obtained successfully, which might reflect the changes of crystal growth conditions, such as the chemical composition of the melt and the rotating and pulling speeds, and the temperature distributions in the crucible and furnace.5.The system has been applied to characterization of a proton-exchnged layr fabricated on Z-cut MgO (5mol%) : LiNbO_3 substrate with a layr thickness of 0.5 mum. It has been demonstrated that the system has the capability to resolve the change of diffusion depth of 2 nm and the change of extraordinary refractive index of 5x10^<-4>. It has been suggested that this method should be adapted as a new analytical technique for development and evaluation of waveguide-type optical device fabrication processes and systems for the future mass production. Less