扫描近场光学显微镜探针与光场相互作用的分析

采用时域有限差分方法对镀金属膜光纤探针在近场光探测中对光场产生的扰动和相互作用过程进行了数值分析。选择纳米孔径的隐失场光场和镀金属膜光纤探针建立了近场光探测的理论模型,讨论了探针孔径尺寸、扫描高度等因素对光场探测的影响,以及测量光场与初始光场之间的关系等。研究结果表明,当探针孔径尺寸与待测纳米孔径尺寸相当,探针扫描高度在接近探针孔径尺寸的一半时,测量得到的光场分布数据能够准确描述初始光场分布。     

层析成像图像重建算法综述

介绍了层析成像技术的图像重建算法,并从正向问题数学模型的简化和反向问题数学模型的映射结构的角度比较了各种算法的特点和优劣。研究表明:用本质是线性算法的各种变换方法重建图像存在严重失真,而卷积滤波的引入可以使变换方法的重建效果有所改善;基于导数搜索的迭代算法对初始值依赖性强、收敛速度慢并且容易陷入局部最优解;基于Fourier变换的方法具有本质的局限性;小波变换则可以同时刻画图像时域和频域的细节特征;有限元法通过重建对象像素的智能划分可以简化正问题的复杂性;而具有物理背景的蒙特卡罗法、模拟退火法、遗传算法、粒子滤波法及神经网络法更适合于复杂且非线性的图像重建;智能化、仿生化、并行化以及各种算法的融合是层析成像图像重建算法的发展趋势。     

TL16C550在一种新型光纤陀螺中的应用

再入式光纤陀螺使相互干涉的两路光在干涉之前循环进入Sagnac光纤敏感环。介绍了这一新型光纤陀螺的原理,采用专门的异步串行通信芯片TL16C550扩展DSP串口,实现陀螺与导航计算机的通讯。结果表明陀螺的数据输出可以达到1kHz,能实现陀螺与导航计算机之间的快速、稳定、准确的数据传输。研制的陀螺零偏稳定性为4.5°/h。     

用于绝对距离测量的波长扫描干涉仪信号分析

提出了一种可用于绝对距离测量的波长扫描光纤干涉仪。在时域和频域上，对其输出信号进行了研究。理论分析了法布里－珀罗腔多光束干涉所产生的干扰以及扫描过程中波长的随机漂移对输出信噪比的影响。由此提出了外腔光源结构和加工精度的要求，并设计了相应的信号处理算法，达到了距离测量所要求的０．０５μｍ的精度和０．０１μｍ的分辨率     

Contrastive study of two SESAMs for passive mode-locking in Nd:YVO_4 laser with low pump power

Two semiconductor saturable absorber mirrors (SESAMs), of which one is coated with 50% reflection film on the top and the other is not, were contrastively studied in passively mode-locked solid-state lasers which were pumped by low output power laser diode (LD). Experiments have shown that reducing the modulation depth of SESAM by coating partial reflection film, whose reflectivity is higher than that between SESAM and air interface, is an effective method to get continuous wave (CW) mode-locking instead of Q-switched mode-locking (QML) in low power pumped solid-state lasers. A simple Nd:YVO4 laser pumped by low power LD, in which no water-cooling system was used, could obtain CW mode-locking by the 50% reflector coated SESAM with average output power of ~ 20 mW.     

Comparison between Two Kinds of Semiconductor Absorbers for Mode-Locking in Nd：YVO4 Laser

We have demonstrated passive mode-locking in a diode-end-pumped Nd：YV04 laser using two kinds of semiconductor absorbers whose relaxation region comes from Ino.2sGao.75As grown at low temperature （LT） and GaAs/air interface respectively. Mode-locking, using absorbers of the GaAs/air interface relaxation region, has the characteristics of less Q-switching tendency and higher average output power than that using absorbers of LT In0.25Ga0.75As relaxation region, but is not as stable as the latter.     

半导体泵浦固体激光陀螺的研究进展

本文对半导体泵浦固体激光陀螺近年来研究进展作了分析和评述，表明半导体泵浦固体激光陀螺是一种全新可行的激光陀螺方案。     

光纤传感技术在腐蚀监测中的应用

本文全面介绍了利用光纤传感技术检测与材料腐蚀相关参数的检测方法和应用状况;系统地分析了各项技术的优缺点及国内外发展状况;明确提出参数的综合检测是材料所处环境的腐蚀状况的全面评估措施,它为腐蚀防护提供了理论依据。     

Experimental research on the longitudinal field generated by a tightly focused beam

The longitudinal optical field is a peculiar physical phenomenon that is always involved with the domain of near-field optics. Due to its extraordinary properties, it has recently attracted increasing attention in research and application. In this work, the longitudinal fields generated by the evanescent illumination of tightly focused, different polarized hollow beams are investigated. The focused light fields are numerically simulated according to vector diffraction theory, and their vector analysis is also carried out. The longitudinal fields on the focal plane are demonstrated experimentally using tip-enhanced scanning near-field microscopy. The simulation and experimental results show that the tightly focused radially polarized beam is suited to generating a stronger and purer longitudinal optical field at the focus.     

阶梯型纳米孔径的近场光学局域增强特性研究

提出一种高分辨力与高通光效率兼备的阶梯型纳米孔径设计方法 ,孔径的尺寸从膜层的入射表面向出射表面呈阶梯型逐渐减小 ,直到在膜层的出射表面形成一个亚波长的小孔。采用三维时域有限差分 (FDTD)方法对方形阶梯型纳米孔径及三角形阶梯型纳米孔径进行了数值模拟计算。结果表明 ,由于近场光学很强的局域场增强效应 ,其通光效率与输出光强极大值在具有相同近场光斑尺寸情况下 ,较普通的非阶梯型纳米孔径提高了两个数量级 ,甚至更高 ,有效地提高了输出光功率。采用四台阶三角形阶梯型纳米孔径 ,当光斑半峰全宽为 97nm× 74nm时 ,出射光强极大值达到 10 4 9.76 ,较入射光增强了 10 0 0倍 ,而通光效率大于 1,达到 1.6 7。这种阶梯型纳米孔径可以直接作为纳米孔径激光器的出射孔径提高其输出光功率 ,也可以作为独立的光学屏对入射光进行整形得到具有高输出功率的亚波长尺度光源 ,在纳米尺度光学成像、光谱探测、数据存储、光刻、光学操作等近场光学应用领域具有潜在的应用前景。