一种低速、连续、单色性好的冷原子束

本文提出一种利用磁光阱冷却捕获技术制备低速、连续、单色性好原子束的方法及技术.采用3维磁光阱从背景Rb蒸汽中捕获Rb87原子进行冷却、捕获形成原子云团,利用在纵向方向上结构设计的小孔将冷原子云团推出形成冷原子束,并在原子束行进方向上采用2维光学黏胶对原子束进行准直,采用态制备激光对其进行态制备,全部制备到Rb87原子的基态能级|F=1>上,从而为原子惯性技术(原子干涉仪、原子重力仪、原子加速度计)、原子频标(原子钟)提供低速、连续、单色性好的原子束.文章对于制备技术的实验系统及实验结果进行了详细的阐述.     

高通量冷原子束流的实现与测量

我们在实验上基于铯原子的2D+磁光阱获得了通量为8.5×1010原子/s、平均速度与速度分布分别为16 m/s与4 m/s、空间发散角为25 mrad的冷原子束流,通过相敏的飞行时间法对原子束流的通量进行了准确测量,并对背景原子气压、推送光功率以及冷却光失谐等参量对原子束流的影响进行了实验研究与分析.     

二维磁光阱产生铯原子束的数值模拟

通过分析铯原子在σ+-σ-组态的圆偏振光照射下塞曼子能级的分布情况,构造铯原子在二维磁光阱(2D-MOT)中的受力模型,利用龙格-库塔方法求解铯原子的运动方程,实现原子束产生过程的三维模拟。得出原子束流量随小孔半径、铯原子蒸汽压、激光光强、激光失谐量、磁场梯度等的变化规律。与实验数据进行比较表明受力模型的正确性, 该方法能直观模拟原子束的产生,准确揭示原子束流量随各项参数的变化规律,为实验提供理论指导。     

二维磁光阱产生铯原子束的数值模拟

通过分析铯原子在σ~+-σ~-组态的圆偏振光照射下塞曼子能级的分布情况,构造铯原子在二维磁光阱(2D-MOT)中的受力模型,利用龙格-库塔方法求解铯原子的运动方程,实现原子束产生过程的三维模拟.得出原子束流量随小孔半径、铯原子蒸汽压、激光光强、激光失谐量、磁场梯度等的变化规律.与实验数据进行比较表明受力模型的正确性,该方法能直观模拟原子束的产生,准确揭示原子束流量随各项参数的变化规律,为实验提供理论指导.     

在芯片表面囚禁冷极性分子的多功能静电阱EI北大核心CSCD

提出了一种用一对金属平板电容器和4根半埋入绝缘介质的杆电极组成的用于囚禁处于弱场搜寻态的冷极性分子的静电表面阱方案。用有限元软件计算了单阱囚禁时的空间电场分布,发现芯片表面上方2.2 mm左右形成了一个三维封闭的静电阱。选用重氨(ND_3)分子作为测试分子,用经典的蒙特卡罗方法模拟了ND_3分子被装载和囚禁的动力学过程。模拟结果表明,当ND_3分子束中心速度为13m/s、装载时刻为0.576ms时,最大装载效率可达53%,被囚禁的冷极性分子的温度约为35mK;如果继续增大平板电极的电压,则原先的单阱将对称分裂为两个阱,两个阱中的分子数目比为1…1;通过改变中间两个杆电极的电压,可实现非对称分裂,以此来调节两阱中囚禁分子数目比;可实现在0%~100%范围内左阱和右阱的分子数目占总分子数目的比例的调节。该方案为进一步研究三维囚禁型冷极性分子静电表面干涉仪打下基础,对于精密测量和研究物质波干涉有着重要的意义。     

冷原子的横向推载与探测

文中在获得温度低,数目多的冷原子基础上,研究了冷原子传输速度与推的脉冲光各种参数之间的关系.     

采用Damman光栅实现冷原子或冷分子囚禁的光阱阵列

提出了一种采用Damman光栅和球面透镜组合光学系统产生二维光阱阵列的新方案. 在使用红失谐高斯激光束照射的条件下，推导了计算光阱阵列的周期、光强分布、光强梯度和光阱几何参数的经验公式，讨论了此光阱阵列的特点以及在原子光学和分子光学中的应用. 研究结果表明，这种光阱阵列方案比已有的光阱阵列方案更为简单可行、操作方便，非常适用于冷原子或冷分子的阵列囚禁，以及制备新颖的光学晶格. 关键词： 冷原子或冷分子 光阱阵列 Damman光栅 光偶极势     

新颖操控冷原子/冷分子的组合三光学阱新方案及实验研究

提出了一种构建可囚禁与操控三种冷原子或冷分子样品的光学三阱组的新方案,该方案采用常用的液晶空间光调制器作为分光器件,分光调制函数类似于二元相位光栅;对提出的方案进行了模拟实验,并研究了从光学三阱到单阱的双向演化过程。该光学三阱的模拟实验结果与理论方案相符,三阱的操控性好,有利于三种不同的冷原子或冷分子样品的装载与操控等相关实验研究。     

利用补偿线圈提高塞曼减速器效率的理论及实验研究

研究了用于锶原子光晶格光钟原子冷却的塞曼减速器,应用增添补偿线圈的方法可以延长减速器的有效减速距离和增大减速器末端的磁场梯度,进而增加一级冷却俘获锶原子的数目,理论分析采用该方法实现的塞曼减速器较使用单一线圈塞曼减速器可以增加31.17%的俘获原子数目;飞行时间法测量了减速前后原子束中原子的速度分布,原子的最可几速度由380m/s降为43m/s,分布线宽相应变窄。荧光法测量俘获原子数目表明在相同实验条件下,应用补偿线圈后磁光阱俘获原子数目从1.26×106提高到1.81×106,增加30.4%。     

利用蓝失谐激光诱导微型光学偶极阱中冷原子间的光助碰撞提高单原子制备概率

借助于微米尺度的远失谐光学偶极阱(FORT)中蓝失谐光的光助碰撞效应与反馈控制系统,文章在实验上实现了FORT中单个原子的高效制备.结合原子的势能曲线,分析了原子在红失谐光和蓝失谐光作用下的光助碰撞效应,并且在实验上得到红失谐光诱导下单原子的制备概率约50%,蓝失谐光诱导下单原子的制备概率约80%.通过反馈控制系统,当原子数目小于1时,反馈控制使磁场梯度减小以快速俘获原子,当原子数目大于1时,反馈控制开启蓝失谐光场,使得原子一个个逃逸出阱中,最终实现了FORT中单原子的制备概率约95%,为下一步偶极阱的二维扩展奠定了基础.通过HBT实验测量FORT中单原子发出光子的统计特性,得到二阶相干度g(2)(τ=0)=0.08.     

Nonparaxial Dark-Hollow Gaussian Beams

The concept of nonparaxial dark-hollow Gaussian beams （DHGBs） is introduced. By using the Rayleigh-Sommerfeld diffraction integral, the analytical propagation equation of DHGBs in free space is derived. The on-axis intensity, far-field equation and, in particular, paraxial expressions are given and treated as special cases of our result. It is shown that the parameter f = 1/κω0 with κ being the wave number and ω0 being the waist width determines the nonparaxiality of DHGBs. However, the parameter range, within which the paraxial approach is valid, depends on the propagation distance. The beam order affects the beam profile and position of maximum on-axis intensity.     

Gaussian Beams of Gravitational Wave

The standard and high-order Gaussian beam solutions for gravitational wave is obtained in the linear approximation of vacuum Einstein equation under harmonic conditions.     

Gaussian Beams of Gravitational Wave

The standard and high-order Gaussian beam solutions for gravitational wave is obtained in the linear approximation of vacuum Einstein equation under harmonic conditions.     

Scalar Approximation of Super-Gaussian Beams

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平顶高斯光束的传输特性

将平顶高斯光束作为一个整体光束处理 ,研究了它通过近轴 ABCD光学系统的传输特性。对无光阑情况 ,推导出较为普遍的解析式 ;而对有光阑限制情况 ,数值积分是可行的。给出的典型数值计算结果证实了这种方法与有限拉盖尔 -高斯函数展开法是等价的。     

Diffractive Multifocal Focusing of Gaussian Beams

The problem of diffraction of a spherical wave with Gaussian amplitude distribution on two infinitesimally thin and ideally reflecting screens with apertures on an optical axis is solved within the quasi-optical approximation. It is shown that when a Gaussian beam illuminates a bicomponent diffraction system with small Fresnel numbers in a near zone of the second screen, the effect of diffractive multifocal focusing of radiation is observed. In this case, the diffraction picture from the second screen in the focal planes represents the circular nonlocal bands of the Fresnel zones with a bright narrow peak at the center, whose intensity can exceed by six times the value of the incident wave intensity. The energy efficiency of diffractive focusing of Gaussian beams by the bicomponent diffraction system can be as high as 70%. The proposed diffractive method allows the focusing of the wide-aperture beams without using classical refraction elements such as lenses and prisms, and it is applicable to both low-intensive and high-power radiation.     

Diffractive Multifocal Focusing of Gaussian Beams

The problem of diffraction of a spherical wave with Gaussian amplitude distribution on two infinitesimally thin and ideally reflecting screens with apertures on an optical axis is solved within the quasi-optical approximation. It is shown that when a Gaussian beam illuminates a bicomponent diffraction system with small Fresnel numbers in a near zone of the second screen, the effect of diffractive multifocal focusing of radiation is observed. In this case, the diffraction picture from the second screen in the focal planes represents the circular nonlocal bands of the Fresnel zones with a bright narrow peak at the center, whose intensity can exceed by six times the value of the incident wave intensity. The energy efficiency of diffractive focusing of Gaussian beams by the bicomponent diffraction system can be as high as 70%. The proposed diffractive method allows the focusing of the wide-aperture beams without using classical refraction elements such as lenses and prisms, and it is applicable to both low-intensive and high-power radiation.     

Beams generated by Gaussian quasi-homogeneous sources

An explicit expression is presented for the cross-spectral density function of the light in any cross-section perpendicular to the axis of a beam generated by a planar, steady-state, quasi-homogeneous source, whose intensity distribution and degree of spatial coherence are both gaussian. The result is used to discuss some properties of such a beam. It is found, in particular, that the ratio of the transvers (spatial) coherence length of the light to the beam width is the same for every cross-section perpendicular to the beam axis.     

Propagation Characteristics of Exponential-Cosine Gaussian Vortex Beams

We propose a controllable exponential-Cosine Gaussian vortex(ECGV) beam,which can evolve into the different beam profiles with three parameters:distance modulation factor(DMF),split modulation factor(SMF) and rotation modulation factor(RMF).When SMF is 0,the ECGV beam appears as a perfect single-ring vortex beam and the ring radius can be adjusted by the DMF.We deduce from mathematics and give the reason for the single-ring characteristics.When SMF is not 0,the beam splits symmetrically.DMF,SMF ...     

双A共振原子系统中两脉冲光束的同时慢光传输

在热的铯原子汽室中,借助双A共振四波混频效应,实验研究了入射探针光脉冲和产生的共轭光脉冲的同时慢光传输特性.实验中首先将泵浦光锁定在铯原子D1线超精细跃迁F=4→F'=3上,将探针光调至超精细跃迁F=3→F'=3附近扫描,通过对探针光和共轭光增益特性的分析,给出获得最大增益所对应的最佳铯泡温度约110℃.最后,采用365 ns高斯脉冲作为入射探针光脉冲,研究了探针光脉冲和共轭光脉冲的延迟时间与双光子失谐的关系.通过改变双光子失谐,探针光脉冲的延迟时间可以从40 ns增加到343 ns,相应的群速度从1 875 km/s减小到219 km/s;产生的共轭光脉冲的延迟时间可以从12 ns增加到159 ns,相应的群速度从6 250 km/s减小到472 km/s.