Optical homogeneity of ADP crystals from rapid growth

ADP (NH₄H₂PO₄) crystals were grown through the traditional method and rapid growth technology. The optical homogeneity of rapid grown ADP crystals was analyzed by laser interferometry and X-ray topography. Laser interferometry revealed sector boundaries at which optical homogeneity decreased dramatically. The main defects that seriously reduced the optical homogeneity of the rapid grown ADP crystal were sector boundaries, growth bands and inclusions. The concentration of Fe and Cr impurities was tested by a plasma emission spectrometer. It was found that the preferential incorporation of metallic impurities into the prismatic faces resulted in high density of growth bands and inclusions, thus reducing optical homogeneity of the prismatic sector.     

Study on the micro-region structure and properties of two dithienothiophene-dicarboxylic acids

Self-organized dithieno [3,2-b:2',3'-d] thiophene-2,5-dicarboxylic acid (A) and dithieno [2,3-b:3',2'-d] thiophene-2,5-dicarboxylic acid (B) films were prepared through solvent-induced order-disorder transition method.The arrangement of the two molecules on substrates were observed by atomic force microscopy (AFM),which demonstrated that A was arranged orderly in a certain angle on mica,while B was flat-flying on mica.The optical and conductance properties in micro region of these two compound films were ch...     

Influence of the cobalt concentration on optical and magnetic properties of zinc oxide

A series of Co-doped ZnO thin films have been prepared by direct current reactive magnetron sputtering on glass substrates.The structural characterization by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) gave no evidence of second phase formation.The qualitative composition and chemical state were characterized by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectronic spectrometry (XPS),respectively.The results confirmed that Co was incorporated as Co3+,occupying the ...     

A wide tuning range electro-optic filter based on long-period waveguide grating

We present the design of an electro-optic filter with polarization insensitivity based on a long period waveguide grating. The filter exhibits an ultra-large wavelength tuning range of exceeding 35 nm and covering the whole C band (1530 to 1565 nm) in a bias voltage range from −84 to 84 V. In the whole tuning range, the transmission coefficients for quasi TE modes are over 97% and the 3 dB bandwidths are below 0.8 nm. The wavelength sensitivity to the tunable voltage is about 0.208 nm/V. This electro-optic filter can be used in dynamic WDM networks for fast wavelength scanning/selection, communication channel reconfiguration, and optical switching.     

Matlab仿真辅助光纤通信课程教学研究

针对光纤通信理论教学中涉及复杂数学计算以及不能得到直观物理图像等问题,结合具体的操作实例,将Matlab软件引入光纤通信教学.结果表明,Matlab软件可以将光纤通信课程中抽象的概念和理论用生动直观的图形和动画来演示,这有助于学生理解和掌握课程内容,提高教学效果.     

SDS辅助的种子生长法制备片状纳米银

以4 nm银为种子,SDS为结构导向剂,乙二胺四乙酸二钠为还原剂,采用晶种法在溶液成功的制备了片状银纳米粒子。透射电镜及紫外-可见光谱表征指出所得的产物由厚度小于20 nm的薄的银纳米片构成。利用紫外-可见光谱仪对银纳米片的形成过程进行了研究,并探讨了反应温度、晶种量对表面等离子共振特性的影响。结果表明:温度从60℃升高到80℃可导致银纳米片的等离子共振峰位置和数目发生明显的变化,继续升高温度则无明显的影响;同时,晶种量不仅能影响纳米Ag的尺寸,而且会影响其形成反应速率。     

采用双树复小波和混合概率模型的光学相干层析图像去噪

为了去除光学相干层析图像中的斑点噪声,提出了基于双树复小波变换的混合概率模型ProbShrink算法. 针对原始光学相干层析图像中信号和噪声的分布特点,在微观层面引入了混合概率模型：将OCT图像取对数后进行双树复小波变换,对于层状边缘中与边缘点“方向一致”的小波系数,采用广义高斯模型描述;对于其他小波系数,则采用高斯模型进行描述. 而后采用改进的ProbShrink算法进行去噪. 实验结果表明,该算法在大幅提升信噪比的情况下保持边缘锐度的相对稳定,优于传统的基于小波变换的去噪方法.     

毫米波光载射频系统研究的新进展

论述毫米波光载射频（radio over fiber,RoF）系统研究的新进展.发展了基于光学倍频（optical frequency multiplication,OFM）概念的毫米波光学生成理论与技术,包括通过电光调制器的高阶光波边模形成、光探测器自外差射频(radio frequency,RF)产生方法的推导、双向毫米波RoF系统的设计等;提出中频正交频分复用（orthogonal frequency division multiplexing,OFDM）毫米波调制的新方案,对光调制器非线性造成的OFDM信号的失真建立完整的数学模型,优化光调制度;同时,实现双向40 GHz RoF实验系统,传输速率达到100 Mbit/s.     

CPML在脉冲辐射场数值模拟中的应用研究

利用时域有限差分法对电磁脉冲模拟器辐射天线产生的电磁场进行数值模拟,在分析卷积完全匹配层(CPML,convolutional perfectly matched layer)原理的基础上,分别选用CPML和修正的完全匹配层(MPML)两种吸收边界条件进行对比分析,仿真结果表明CPML不仅可以吸收传播模,而且还能够有效吸收低频凋落波,获得了很好的截断效果,展示了其在电磁脉冲模拟器数值模拟中的应用前景。     

四轴五框架车载稳定平台稳定性的仿真分析

针对车载稳定平台水平扰动较大、方位扰动较小的特点,提出一种四轴五框架结构的车载稳定平台,由一级水平稳定与二级两轴三框架稳定实现对车体水平扰动的双重抑制。通过平台运动学及动力学分析,建立一级水平稳定、二级两轴三框架稳定与整体四轴五框架稳定平台的数学模型,进而对稳定平台抑制车体扰动的特性进行分析。在车体典型的三种振动环境下对四轴五框架结构的稳定平台与两轴三框架结构的稳定平台稳定效果进行仿真,结果表明四轴五框架结构的稳定平台比两轴三框架稳定平台稳定精度提高一倍。