Novel inspection of welded joint microstructure using magneto-optical imaging technology

A novel method for measuring differences of microstructure by advanced use of the Faraday magneto-optical effect is proposed. Two groups of YAG laser welds on Q235 have been investigated in order to compare MO imaging and traditional methods. Microstructure images have been compared with MO images, and MO diagrams display different colors and gray scales for the base metal, the weld zone, and the heat affected zone. Experimental results indicate that the welded joint microstructure can be inspected by MO imaging without metallographic preparation.     

Investigating the vortex melting phenomenon in BSCCO crystals using magneto-optical imaging technique

Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals of Bi₂Sr₂CaCu₂O₈ (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface with varying field (H)/temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder/inhomogeneities across the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local melting temperature/field, we have constructed maps of the melting landscape T _m(H, r), viz., the melting temperature (T _m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite effects on the local melting transition.     

基于扭秤的激光干涉差动测量微小冲量方法

基于扭秤测量冲量原理,结合激光干涉法差动测量角度的方法,提出一种基于扭秤的激光干涉差动测量微小冲量的方法。介绍系统的基本组成和测量过程,给出扭秤结构设计参数,并对系统参数进行了标定,结合设计参数与标定结果,对系统的分辨率、量程和精度进行了校核,在典型的测量环境下,对激光烧蚀靶材所形成的Ns量级微小冲量进行了测量,给出了典型的测量结果并进行分析。结果表明:所提出的基于扭秤的激光干涉差动测量微小冲量方法,系统分辨率可达10-7Ns量级,测量范围跨5个数量级,最大可以测量10-2Ns量级冲量,测量精度优于95%。     

用吸收法对铯原子磁光阱中冷原子数目的测量

介绍了吸收法测量冷原子数的原理以及对铯原子气室磁光阱中俘获的冷原子数目的测量过程及结果. 与通常的荧光收集法相比，在原理上与静止二能级原子同共振单模光场作用的模型更加接近，同时大大减小了测量中的误差累积，提高了测量精度. 测得的冷原子数为(8±0.3)×10⁶，同时还利用测得的阱中俘获的稳态冷原子数和磁光阱中冷原子的寿命间接获得了磁光阱的俘获率. 关键词： 激光冷却与俘获 磁光阱 冷原子数目 俘获率     

Independently tunable transmission-type magneto-optical isolators based on multilayers containing magnetic materials

We investigate the magneto-optical (MO) properties of multilayers containing several magnetic defects. Our numerical simulations show that each MO defect mode can be tuned independently by adjusting the structural parameters of magnetic materials. In addition, giant Faraday rotation can be obtained. Our results indicate that the structure may have potential applications for independently tunable multichannel MO isolators.     

光致原子解吸附对冷原子磁光阱装载的动力学研究

在获得光致原子解吸附(light-induced atom desorption,LIAD)效应的基础上,从理论和实验方面分析了LIAD对铯原子磁光阱装载的动力学过程的影响,特别是背景原子对磁光阱的影响.通过实验获得了不同光强和照射时间下关闭解吸附光后磁光阱中铯原子的衰减过程,理论模型定量地描述了背景铯原子造成压强的变化及其对最终平衡态下真空度的影响.该研究对中性原子的长时间俘获,有效控制磁光阱中原子的装载过程具有重要意义. 关键词： 光致原子解吸附 磁光阱 激光冷却与俘获     

抽运-检测型非线性磁光旋转铷原子磁力仪的研究

报道了一种抽运-检测型的非线性磁光旋转铷原子磁力仪.其原理是线偏振光通过处于外磁场环境中被极化的原子介质后,由于原子对线偏振光中左、右圆偏成分不同的吸收和色散,导致光的偏振方向会产生与磁场相关的转动.分析了该磁力仪的工作原理,并测试了它对不同磁场大小的响应.测试结果表明,磁力仪测量范围为100—100000 nT,极限灵敏度为0.2 p T/Hz~(1/2),磁场分辨率为0.1 p T.进一步研究了不同磁场下原子系综极化态的横向弛豫时间,讨论了原子磁力仪高磁场采样率的获得方法.本文的原子磁力仪在5000—100000 n T的磁场测量范围内磁场采样率可实现1—1000 Hz范围内可调,能够测量低频的微弱交变磁场.本文的研究内容为大磁场测量范围、高灵敏度、高磁场采样率的原子磁力仪研制提供了重要参考.     

偏振无关的旋光双反射结构的实验研究

完成了偏振无关双旋光晶体双反射结构的实验研究. 根据其偏振补偿特点对双旋光晶体双反射结构进行简化, 提出了一种偏振无关的单旋光晶体双反射结构. 实验表明, 两种反射结构的偏振保持度均能达到99.97%以上. 作为对比, 分别测试了单个反射镜反射90°和两个反射镜反射90°时的输出光偏振态. 该条件下, 无保偏处理的反射镜的偏振保持度分别只有92.1%和76.2%. 关键词： 偏振态 偏振无关反射 旋光晶体     

Development of surface magneto-optical imaging method

We have observed single vortices in a NbTiN thin film by using magneto-optical (MO) imaging method, in which the light reflected from the surface of the sample produces MO contrasts. The gap between the sample and the indicator film is estimated by the Newton ring and curve fitting to the flux density profile of single vortices.     

中性汞原子磁光阱装载率的优化

量子投影噪声是影响光晶格钟的一个重要参数,提高磁光阱中装载率有利于降低量子投影噪声,可提升光晶格钟的性能.针对实验所用的汞原子单腔磁光阱,本文分析并计算了磁光阱中汞原子受力情况和一维运动规律,在此基础上用随机数方法对磁光阱中汞原子三维装载进行了数值计算,获得了磁光阱中的稳态原子数,研究了磁光阱的冷却激光的光强、失谐量以及磁场梯度等参数对稳态原子数的影响,得出了获得最优装载率的实验参数.涉及的计算方法和结论对汞原子光晶格钟的实验设计具有参考价值.     

Improvement on the magneto-optical Kerr effect of cobalt film with a quadrilayer structure

The magneto-optical Kerr effect of the HfO2 /Co/HfO2 /Al multilayer structure is investigated in this work, and an obvious cavity enhancement of the Kerr response for the HfO2 semiconductor is found both theoretically and experimentally. Surprisingly, a maximum value of about -3 ° of the polar Kerr rotation for s-polarized incident light is observed in our experiment. We propose that this improvement on the Kerr effect can be attributed to the multiple reflection and optical interference in the cavity, which can also be proved by simulation using the finite element method.     

基于PASCO平台的法拉第磁光效应实验

基于PASCO实验平台设计了能在弱磁场下完成的法拉第磁光效应实验,实验装置简单易操作,并能较准确地测定费尔德常量和电子的比荷等.     

基于路径跟踪的水下焊接V形焊缝识别中强干扰的去除

介绍机器人水下焊接V形焊缝图像处理中基于模糊推理的阈值自动选取的算法,提出基于路径跟踪的强干扰的去除方法.制作9种不同形状的窗口模板,以列扫描方式求取这些窗口所覆盖的区域内最大的平均灰度值,同时获取取得最大灰度平均值时的垂直方向的位置,然后根据获取的最大平均灰度值以及相邻区域最大平均灰度值的改变量进行模糊推理,判断获得这些窗口所覆盖区域的阈值.最后跟踪取得最大灰度平均值时的所有位置,在最低位置以下以及最高位置以上检测经阈值处理后的白点,可以消除因水泡、较强弧光形成的干扰.     

显微成像检测表面粗糙度

介绍了用显微成像检测表面粗糙度的方法。该方法具有直观，操作简单，速度快，非接触无损伤，自动检测等优点。显微成像检测表面粗糙度的原理为：被检测表面通过显微放大，由ＣＣＤ作为接收器，经图像采集卡和微机进行数据采集与处理，计算后得到相应的粗糙度。这种方法用于机械加工表面，喷涂等表面检测，对电化学处理表面，指纹，皮肤，细胞等细微结构的检测更具有优越性。     

Intense source of cold cesium atoms based on a two-dimensional magneto–optical trap with independent axial cooling and pushing

We report our studies on an intense source of cold cesium atoms based on a two-dimensional(2D) magneto–optical trap(MOT) with independent axial cooling and pushing.The new-designed source,proposed as 2D-HP MOT,uses hollow laser beams for axial cooling and a thin pushing laser beam to extract a cold atomic beam.With the independent pushing beam,the atomic flux can be substantially optimized.The total atomic flux maximum obtained in the 2D-HP MOT is4.02 × 1010atoms/s,increased by 60 percent compared to the traditional 2D+MOT in our experiment.Moreover,with the pushing power 10 μW and detuning 0Γ,the 2D-HP MOT can generate a rather intense atomic beam with the concomitant light shift suppressed by a factor of 20.The axial velocity distribution of the cold cesium beams centers at 6.8 m/s with an FMHW of about 2.8 m/s.The dependences of the atomic flux on the pushing power and detuning are studied in detail.The experimental results are in good agreement with the theoretical model.     

光学成像法和穿孔法测量飞秒激光焦斑特征

超短超强激光焦斑参数的精确测量是深入开展精密物理实验的前提。在SILEX-Ⅰ激光装置上,采用光学成像法和穿孔法测量了μJ级能量下的激光焦斑特性,采用光学成像方法得到了激光主瓣大小及能量集中度信息,通过穿孔法得到了激光能量透过率与不同大小孔径的关系曲线,并对两种方法得到的测量结果进行了比对研究。研究结果表明,光学焦斑测量法和穿孔法都可以比较准确地反映激光焦斑的能量分布情况,得到的能量分布偏差小于10%。     

Dependence of loading time on control parameters in a standard vapour-loaded magneto-optical trap

Loading time is one of the most important dynamic characteristics of a magneto-optical trap. In this paper, we primarily report on a detailed experimental study of the effects of some magneto-optical trap control parameters on loading time, including the background vacuum pressure, the magnetic field gradient, and the intensities of trapping and repumping lasers. We compare the results with previous theoretical and experimental results, and give qualitative analysis. These experimental investigations offer some useful guidelines to control the loading time of magneto-optical traps. The controllable loading time achieved is helpful to enhance the signal-to-noise ratio of photoassociation spectroscopy, which is remarkably improved from 7 to 28.6.     

漫透射成像法激光强度时空分布测量装置

 提出用CCD漫透射成像法测量激光强度时空分布和激光功率,给出了测量原理, 简要叙述了装置总体结构,介绍了测量装置各部分,给出了散射屏的散射特性,重点分析了光路布局、镜头焦距、光圈、景深、滤光片的参数选择,介绍了数据处理软件,给出了激光强度分布测量实验结果。结果表明：漫透射成像法测量激光强度时空分布是可行的,该装置测量强度分布分辨力高达5 mm;测量功率准确、可靠,测量不确定度小于6%,使用方便,实现了在小空间内对大光斑进行功率和强度分布的同时准确测量。     

Pt974Mn26/Co多层膜的磁性与磁光性质研究

用磁控溅射法制备了Mn含量一定、不同PtMn层厚度的Pt974Mn26/Co磁性多层膜系列，通过x射线衍射对该多层膜系列进行结构分析；测定了不同PtMn层厚度系列样品的磁滞回线、有效垂直各向异性，分析了饱和磁化强度和有效垂直各向异性变化的原因；通过测定该多层膜体系的克尔谱，分析了一定波长下克尔角随PtMn层厚度变化的规律.认为克尔角的变化是由于界面的合金化以及原子的极化减小所致. 关键词： 多层膜 磁性 磁光