An efficient magneto-optical trap of metastable krypton atoms

We report a magneto-optical trap of metastable krypton atoms with a trap loading rate of 3×10(11) atoms/s and a trap capture efficiency of 3×10(-5). The system starts with an atomic beam of metastable krypton produced in a liquid-nitrogen cooled, radio-frequency driven discharge. The metastable beam flux emerging from the discharge is 1.5×10(14) atoms/s/sr. The flux in the forward direction is enhanced by a factor of 156 with transverse laser cooling. The atoms are then slowed inside a Zeeman slower before captured by a magneto-optic trap. The trap efficiency can be further improved, possibly to the 10(-2) level, by gas recirculation. Such an atom trap is useful in trace analysis applications where available sample size is limited.     

Measurement of temperature of laser cooled atoms by one-dimensional expansion in a magneto-optical trap

We discuss a simple time of flight technique for measurement of temperature of a cold cloud in a magneto-optical trap (MOT). The technique is based on spatiotemporal fluorescence imaging of the cloud that is allowed to undergo one-dimensional expansion in the presence of the orthogonal two-dimensional configuration of laser beams by temporal modulation of a pair of counterpropagating trapping beams in the MOT. We show that, in the time scale 0< or =t<5 ms, the expansion of the cloud is ballistic and the temperature can be extracted from the time variation of the rms size of the cloud in the expansion direction. The reliability of the technique has been established by comparing the results with release and recapture method, and also by fitting them to the known temperature scaling law.     

An atomic beam source for fast loading of a magneto-optical trap under high vacuum

We report on a directional atomic beam created using an alkali metal dispenser and a nozzle. By applying a high current (15 A) pulse to the dispenser at room temperature we can rapidly heat it to a temperature at which it starts dispensing, avoiding the need for preheating. The atomic beam produced is capable of loading 90% of a magneto-optical trap (MOT) in less than 7 s while maintaining a low vacuum pressure of <10(-11) Torr. The transverse velocity components of the atomic beam are measured to be within typical capture velocities of a rubidium MOT. Finally, we show that the atomic beam can be turned off within 1.8 s.     

A fibre-optic 3-D microscope with high depth sensitivity

A new fibre-optic microscope with high depth resolution is proposed and experimentally realized. In this microscope, a pair of monomode optical fibre couplers are used to form a six-port all-fibre Michelson interferometer. A lock-in amplifier is used to improve the depth sensitivity and to simplify the optical and electronic circuits. The phase sensing signal is applied to a mirror at one arm of the interferometer. The optimum resolution was about 0?4 nm. The transverse resolution of this microscope is determined by the core diameter of the monomode fibre (9 μm). This 3-D microscope is quite stable to ambient mechanical disturbances, and can be applied to the 3-D microscopy of various biological objects.     

A method for controlling the spins of atoms using optical near-fields

On the basis of the procedure for controlling the spins of atoms using circularly polarized evanescent light proposed by Hori et al.[(1996 ) Abstracts of the 1st Asia‐Pacific Workshop on Near‐field Optics] we discuss the influence of boundary conditions on the probability of spontaneous emission and thus on the spin polarization efficiency, which was not considered in the Hori et al. study. Using the Carniglia–Mandel mode expansion of electromagnetic fields, we derive the spontaneous emission and spin polarization probabilities of atoms near a dielectric surface, and show the atom–surface distance dependence and refractive index dependence. Numerical evaluation for the 6P_1/2–6S_1/2 transition of a Cs atom indicates an increase in the efficiency of spin polarization by 30%.     

采用玻尔兹曼统计法分析光阱刚度的测量精度

考虑高精度的光阱刚度测量是光阱力测量的关键,本文提出了采用玻尔兹曼统计法来分析光阱刚度的测量精度。首先,描述了实验室搭建的近红外光镊系统,并将其搭建在暗室中的气垫平台上,以便隔离光干扰和振动干扰。然后,用四象限光电探测器探测被光镊捕获的微球向后散射的光,并选用与溶液黏度无关的玻尔兹曼统计法计算样品池底面附近的光阱刚度。最后,分析和讨论了溶液温度的变化、四象限光电探测器的灵敏度、采样频率以及采样时间对光阱刚度测量精度的影响。理论分析及实验计算显示:溶液温度的变化对光阱刚度的测量影响很小,但四象限光电探测器的灵敏度对光阱刚度测量精度影响较大。考虑采样的完整性和数据处理速度,采样频率通常取为被捕获颗粒拐角频率的5~10倍。对于本文搭建的近红外光镊测量系统,采样时间取为1~7s时,可以保证高精度地测量光阱刚度。     

An electrostatic glass actuator for ultrahigh vacuum: A rotating light trap for continuous beams of laser-cooled atoms

This article describes the design, characterization, and performance of an electrostatic glass actuator adapted to an ultrahigh vacuum environment (10(-8) mbar). The three-phase rotary motor is used to drive a turbine that acts as a velocity-selective light trap for a slow continuous beam of laser-cooled atoms. This simple, compact, and nonmagnetic device should find applications in the realm of time and frequency metrology, as well as in other areas of atomic, molecular physics and elsewhere.     

Features of the <Superscript>85</Superscript>Rb Spectrum in a Cell with an Antirelaxation Coating

Distortion of the spectrum of the D₁-line of ⁸⁵Rb in optical cells with an antirelaxation coating on the inner walls of the cell is studied. The spectrum shape is found to be significantly dependent on the velocity and direction of changes in the laser frequency. A physical explanation is provided for these features, which are confirmed by numerical simulations. The effect of the magnetic field on the spectrum shape is discussed.     

聚合物包覆改善二维钙钛矿(FPEA)2PbI4光学性能

环境因素（如光照、水蒸气、氧气等）会引发二维钙钛矿材料的降解,其稳定性极大地限制该材料的进一步发展及市场化进程。利用氟化物的强稳定性与疏水性,将其以含氟苯乙胺的形式引入二维钙钛矿的有机层,可以有效地改善二维钙钛矿稳定性,但是荧光效率有所降低。针对这一问题,本文采用聚苯乙烯（PS）、聚甲基丙烯酸甲酯（PMMA）、环烯烃聚合体（COP）三种高分子聚合物对二维钙钛矿薄膜进行包覆,使其荧光强度分别得到2.2、1.3和1.4倍的改善,光照稳定性分别得到3.3、3.1和3.9倍的提升,并进一步验证湿度稳定性。该研究为二维钙钛矿薄膜在光电器件上的开发提供了新思路。     

Pulse shape measurements using single shot-frequency resolved optical gating for high energy (80 J) short pulse (600 fs) laser

Relevant to laser based electron/ion accelerations, a single shot second harmonic generation frequency resolved optical gating (FROG) system has been developed to characterize laser pulses (80 J, ～600?fs) incident on and transmitted through nanofoil targets, employing relay imaging, spatial filter, and partially coated glass substrates to reduce spatial nonuniformity and B-integral. The device can be completely aligned without using a pulsed laser source. Variations of incident pulse shape were measured from durations of 613 fs (nearly symmetric shape) to 571 fs (asymmetric shape with pre- or postpulse). The FROG measurements are consistent with independent spectral and autocorrelation measurements.     

大视场远距离视觉测量系统的分步标定

为了克服工程大视场标定精度不高、标靶加工难度大以及现场操作繁琐的问题,本文基于工业近景摄影测量基本原理提出一种大视场多相机内、外参数的分步标定方法。首先,根据相机透视投影模型,在近距离采用小幅面标靶和角锥体法完成相机前截面内参数的解算;然后,在远距离被测空间内布置若干编码标志点,利用多片后方交会原理计算得到相机外参数;最后,对相机内、外参数进行整体光束平差优化,实现精确标定。为验证该方法的可行性和精度,进行了大视场视觉测量实验,测量结果表明本文标定方法的重投影误差小于0.08像素;外场试验实测10 m直升机旋翼总距角的相对误差小于0.1°。该方法可实现相机内参数标定实验室进行、外参数标定外场完成的操作分离。     

高频激光对化学气相沉积金刚石的大切深实验

为了提高化学气相沉积(Chemical Vapor Deposition,CVD)金刚石的切深,采用新型的声光调制高重复频率激光器,研究了激光功率、焦点位置、激光重复频率、切割线速度以及激光横膜模式对CVD金刚石切缝宽度、切深以及表面粗糙度的影响.研究结果表明:切深和切缝上表面宽随着激光功率的增大而增大;焦点位置随切深...     

Pulse-dilation enhanced gated optical imager with 5 ps resolution (invited)

A 5 ps gated framing camera was demonstrated using the pulse-dilation of a drifting electron signal. The pulse-dilation is achieved by accelerating a photoelectron derived information pulse with a time varying potential [R. D. Prosser, J. Phys. E 9, 57 (1976)]. The temporal dependence of the accelerating potential causes a birth time dependent axial velocity dispersion that spreads the pulse as it transits a drift region. The expanded pulse is then imaged with a conventional gated microchannel plate based framing camera and the effective gating time of the combined instrument is reduced over that of the framing camera alone. In the drift region, electron image defocusing in the transverse or image plane is prevented with a large axial magnetic field. Details of the unique issues associated with rf excited photocathodes were investigated numerically and a prototype instrument based on this principle was recently constructed. Temporal resolution of the instrument was measured with a frequency tripled femtosecond laser operating at 266 nm. The system demonstrated 20× temporal magnification and the results are presented here. X-ray image formation strategies and photometric calculations for inertial confinement fusion implosion experiments are also examined.     

Development of a novel two-dimensional(2D) three-way(3W) fuel flow control servo valve with constant pressure difference

To solve the problems of large volume, and low integration of traditional electro-hydraulic servo valve with constant pressure differential fuel metering device, a new two-dimensional three-way constant pressure differential fuel flow control servo valve (2D3WFFCSV) is developed. It innovatively adopts the advantages of lightweight of “two-dimensional hydraulic technology”, The constant differential pressure function and flow regulation function are integrated into a two-dimensional (2D) main spool with two degrees of freedom (rotational and axial degrees of freedom). The flow control process of 2D3WFFCSV is as follows: firstly, the armature of the torque motor and the two-dimensional piston are coaxially installed at the end of the two-dimensional piston, so the torque motor can directly drive the two-dimensional piston to rotate; secondly the “hydraulic servo screw mechanism”, which can amplify the power, is used to drive the two-dimensional piston to move in line; Finally, a pair of conversion mechanisms (roller group and spiral track conversion mechanism) are converted into the angular displacement of 2D main spool to control the area of flow valve port. The axial degree of freedom of 2D main spool realizes the function of constant differential pressure. To improve the flow control accuracy of the servo valve, the axial position of the 2D piston is detected by the linear displacement sensor (LVDT), and the signal is transmitted to the controller to realize the closed-loop control. To explore its open-loop characteristics, the mathematical models of torque motor, two-dimensional piston and main spool are established to obtain its open-loop transfer function. Then the AMESIM simulation model is built. To optimize the design of the system, through the dynamic simulation of the system, the influence of key parameters on the dynamic response of the system can be studied. An experimental study is carried out to verify the design feasibility of the servo valve. The experimental results show that under the condition of no-load and full-scale input, the closed-loop delay of the servo valve is 1.84%, the linearity is 2.14%, the step response time is 43 ms, and the dynamic frequency response is 38 Hz. The newly developed 2D3WFFCSV has the advantages of high integration, small size, light weight (801.5 g) and high response and control accuracy. It can replace the constant differential pressure, metering valve and hydraulic servo valve in the aeroengine fuel regulator.     

原子力显微镜(AFM)在光盘检测及其质量控制中的应用

综述了原子力显微镜(AFM)在光盘质量检测中的应用.AFM能够在nm尺度上直接对光盘及其模板上的信息位几何结构的特征尺寸及其误差进行三维测量,从而可以建立生产工艺参数和信息位几何结构之间、信息位几何结构和盘片电气性能之间的关系,进而找出影响光盘质量的直接原因.用AFM进行光盘质量检测主要有三方面：盘片和模板表面的定性观测;信息位几何结构的半定量分析;信息位特征尺寸的统计分析.定性观测和半定量分析可以对盘片播放的高误差率、凹坑形态和块出错率、凸台形态及其表面粗糙度等参数进行有针对性的检测;而信息位特征尺寸的统计分析则可以对信息位几何结构的关键参数进行面向生产过程的统计分析.所得结论表明AFM在光盘质量检测过程中具有独特的优势.     

Interferometric determination of the optical properties of fibres with irregular transverse sections (Ramie)

The thickness of fibres and their irregularity were determined from the forward scattering of a He-Ne laser beam. Two methods have been used for the measurement of refractive indices and birefringence of Ramie fibres. The first of these methods is the application of multiple-beam Fizeau fringes in transmission and at reflection. The second is the use of the double refracting interference microscope designed and developed by Pluta. In each method, refractive index values have been determined using two different analyses of the interference pattern. To overcome the difficulty of the irregular transverse section of Ramie fibres, the area enclosed under the fringe shift is considered as representing the path difference integrated across the fibre.     

高分辨力光学微扫描显微热成像系统设计与实现

为提高已研制的基于非制冷焦平面探测器的显微热成像系统的空间分辨力,研究提出了一种基于光学平板旋转微扫描器的高分辨力显微热成像系统.分析了光学平板旋转微扫描的工作原理,给出了微扫描器相关的参数设计、加工容差,并与现有的非制冷显微热成像系统实现了一体化设计与加工,确定了光学微扫描显微热成像系统的技术指标.利用该系统实际采集的显微热图像与过采样处理结果表明系统整体设计的有效性,系统空间分辨力得到提高,可应用于高分辨力显微热分析.＃     

一种结合 TCP 标定的深度相机手眼标定方法

手眼标定是机器人实现视觉引导下精准作业中的关键技术。传统手眼标定和机器人工具中心点(TCP)标定分开进行,存在较大累积误差,同时针对深度相机的手眼标定存在精度不足的缺点。本文提出了一种结合TCP标定过程同步标定深度相机手眼关系的新方法。方法基于深度相机观测和TCP标定相同的标定平面,相机坐标系下标定平面方程和机械臂坐标系下标定平面方程为对应关系,通过平面方程之间的变换来计算手眼关系。本文方法减少了TCP和手眼关系独立标定累积误差影响,节约标定时间和标定件成本。仿真和实测结果表明,本文方法提高了深度相机手眼标定精度,标定后实测位置误差平均为0.2 mm,为机器人视觉控制系统高精度作业所需标定提供了一种新的思路。     

A high performance one-dimensional homodyne encoder and the proof of principle of a novel two-dimensional homodyne encoder

Displacement laser interferometers and interferometric encoders currently are the dominating solutions to the displacement measurement applications which require measurement uncertainties in the order of a few nanometers over hundreds of millimeters of measurement range. But, in comparison with interferometric encoders, to achieve nanometer order or even lower measurement uncertainties, displacement laser interferometers require much stricter environmental control if not vacuum, which will increase their Total Cost of Ownership (TCO). Therefore interferometric encoders are getting more and more preferable. Furthermore, for some applications, the measurement of the out-of-plane displacement is required as well. Therefore, in this work, a one-dimensional interferometric encoder was built and investigated, a novel two-dimensional (one is in-plane, the other one is out-of-plane) interferometric encoder was devised and its principle was proven experimentally. For the one-dimensional encoder, a periodic nonlinearity of ±50 pm with HEIDENHAIN EIB 741 and a periodic nonlinearity of less than ±10 pm with a home built phase meter and off-line Heydemann correction were identified through a comparison measurement with a differential heterodyne interferometer. In addition, this one-dimensional encoder was identified to have a better measurement stability compared to the differential heterodyne interferometer.     

新型QTRAP~(TM)四极杆-线性离子阱串联质谱仪的特点及应用

本文介绍新型QTRAPTM 四极杆 -线性离子阱串联质谱仪的基本原理和主要性能 ;并简述在药物筛选及代谢产物分析、蛋白分析和在天然产物结构分析方面的应用