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。     

以慢原子束方式进行原子转移的双磁光阱系统

建立了一套用于玻色-爱因斯坦凝聚实验的铷原子双磁光阱装置.从低速强源中获得慢原子束，向超高真空磁光阱进行原子转移.低速强源磁光阱与超高真空磁光阱之间可维持3个量级的压强差,超高真空磁光阱的真空度最高可达1×10^-9 Pa. 慢原子束的束流通量达1×10⁹/s. 约4×10⁸个⁸⁷Rb原子被装载到超高真空磁光阱中.还讨论了两种典型情况下磁光阱中装载的最大原子数.     

应用于铯原子喷泉钟的二维磁光阱研制

理论模拟研究了二维磁光阱原子束流量与饱和蒸汽压、冷却光强、激光失谐量的关系, 构建了二维磁光阱(2D-MOT)装置, 实验上实现了大流量的慢速原子束, 其测量值为2.1× 10⁹/s.利用荧光法测量了各实验参数与流量的关系, 测量结果与数值模拟结果符合较好. 关键词： 2D-MOT 流量 慢速原子束 铯原子喷泉钟     

基于二维磁光阱的增强型199Hg冷原子团制备

在精密测量领域中,高效地制备冷原子团具有重要的意义.在光晶格钟里,缩短冷原子团的制备时间可以降低Dick噪声,从而提高光晶格钟的稳定性.本文采用二维磁光阱加推送光的构型提高了三维磁光阱在超高真空环境中的装载率,并通过压缩磁光阱技术降低了原子团温度,实现了用于¹⁹⁹Hg光晶格钟的增强型冷原子团制备.实验上通过优化三维和二维磁光阱的失谐量和磁场梯度以及推送光的失谐量和功率等参数,将三维磁光阱的¹⁹⁹Hg冷原子装载率增强了51倍,提升至3.1×10⁵ s^–1,然后使用压缩磁光阱技术将¹⁹⁹Hg冷原子团的温度降低至45μK,低于多普勒冷却理论温度.这种基于二维磁光阱的增强型冷原子团制备可在超真空环境下实现对三维磁光阱装载率的高增益,有效地缩短了冷原子团的制备时间,同时也降低了原子团的温度,有利于提高光晶格的转移效率,为其他冷原子实验中冷汞原子团制备提供了有效方案.     

磁光阱中超冷钠-铯原子碰撞的实验研究

研究了磁光阱中异核超冷钠铯原子的碰撞机理, 测量了超冷钠原子的碰撞损失率, 得到了钠-铯原子的碰撞损失系数β_Na-Cs与钠原子俘获光强度之间的关系. 利用多普勒模型计算了不同俘获光强度下的钠原子磁光阱的阱深, 得到了临界光强的理论值, 与实验结果符合得较好.     

采用原子汽室磁光阱技术实现铯原子的激光冷却与俘获

近１０年来，中性原子的激光冷却与俘获方面的研究极为活跃，取得了许多重要的进展。其中，１９９０年Ｗｉｅｍａｎ等人提出的直接工作在原子汽室中的磁光阱［１］，相对简化了原子冷却与俘获的装置和技术，使这方面的研究得以进一步推广和促进。由于冷原子在玻色－爱因斯...     

用短程飞行时间吸收谱对铯磁光阱中冷原子温度的测量

介绍采用短程飞行时间吸收谱测量铯原子磁光阱(MOT) 中冷原子温度的基本原理及实验实现.与通常的飞行时间方法不同，采用短程飞行时间吸收谱来测量MOT 中冷原子云的温度.在MOT 区域正下方若干毫米处入射一束圆柱状共振探测光束(实验中对于h=3mm，5mm，8mm的情况均作了研究)，释放冷原子云，在其膨胀和自由下落过程中穿过探测光束，即可由光电探测器测得飞行时间吸收谱，由此推得MOT中冷原子的温度. 关键词： 磁光阱 冷原子 飞行时间 短程飞行时间 铯原子     

大磁场梯度铯原子磁光阱中单原子的实验观测

基于中性原子的激光冷却与俘获技术,目前人们已可以对单个原子的外部乃至内部自由度进行有效的调控.从而可在单原子单光子的层次上对光场与物质的相互作用进行研究.     

铯原子双磁光阱中冷原子的输运：从推载到导引

在超高真空环境下实现中性原子的激光冷却与俘获，可以有效地避免背景气体对冷原子的碰撞所造成的影响，已成为玻色-爱因斯坦凝聚、冷原子光学腔量子电动力学、中性原子玻色-费米混合气体等实验研究的出发点。结合气室磁光阱和超高真空磁光阱的所谓双磁光阱，以其真空系统相对简单、参数易于控制、效率高等优点，得到了很大发展。双磁光阱既能在气室磁光阱部分从处于室温的原子背景中快速冷却和俘获原子，然后将其通过一定途径输运到超高真空磁光阱中，又能达到在压力极低的超高真空环境下制备冷原子的目的。     

Enhanced cold mercury atom production with two-dimensional magneto-optical trap

A cold atom source is important for quantum metrology and precision measurement. To reduce the quantum projection noise limit in optical lattice clock, one can increase the number of cold atoms and reduce the dead time by enhancing the loading rate. In this work, we realize an enhanced cold mercury atom source based on a two-dimensional (2D) magneto-optical trap (MOT). The vacuum system is composed of two titanium chambers connected with a differential pumping tube. Two stable cooling laser systems are adopted for the 2D-MOT and the three-dimensional (3D)-MOT, respectively. Using an optimized 2D-MOT and push beam, about 1.3×10⁶ atoms, which are almost an order of magnitude higher than using a pure 3D-MOT, are loaded into the 3D-MOT for ²⁰²Hg atoms. This enhanced cold mercury atom source is helpful in increasing the frequency stability of a neutral mercury lattice clock.     

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     

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.     

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.     

Continuously transferring cold atoms in caesium double magneto-optical trap

We have established a caesium double magneto-optical trap (MOT) system for cavity-QED experiment, and demonstrated the continuous transfer of cold caesium atoms from the vapour-cell MOT with a pressure of ～ 1×10^-6 Pa to the ultra-high-vacuum (UHV) MOT with a pressure of ～ 8×10^-8 Pa via a focused continuous-wave transfer laser beam. The effect of frequency detuning as well as the intensity of the transfer beam is systematically investigated, which makes the transverse cooling adequate before the atoms leak out of the vapour-cell MOT to reduce divergence of the cold atomic beam. The typical cold atomic flux got from vapour-cell MOT is ～2×10⁷ atoms/s. About 5×10⁶ caesium atoms are recaptured in the UHV MOT.     

Efficient generation of cold atoms towards a source for atom lithography

We report on the efficient generation of cold rubidium atoms as a potential coherent atom source for atom lithography. We successfully trapped and cooled 2.6 × 10⁸ atoms in 5 s with a conventional magneto-optical trap simply by enlarging the diameter of the laser beam to 20 mm. The size of the laser-cooled atom cloud was measured to be 10 × 7 × 7 mm³. The number of trapped atoms was approximately 10 times as large as that of previous typical results, while the loading time of atoms remained the same.     

Investigation of ultracold atoms and molecules in a dark magneto-optical trap

In this paper,ultracold atoms and molecules in a dark magneto-optical trap(MOT) are studied via depumping the cesium cold atoms into the dark hyperfine ground state.The collision rate is reduced to 0.45s-1 and the density of the atoms is increased to 5.6×1011cm-3 when the fractional population of the atoms in the bright hyperfine ground state is as low as 0.15.The vibrational spectra of the ultracold cesium molecules are also studied in a standard MOT and in a dark MOT separately.The experimental results are analyzed by using the perturbative quantum approach.