一种新颖的实现冷原子或冷分子囚禁的可控制光学四阱及其二维光学晶格

原子光学晶格为精确操控中性原子和研究某些基本物理问题提供了一种方法。提出了一种利用单光束照明余弦型振幅光栅与透镜组合系统实现冷原子或冷分子囚禁的可控制光学四阱新方案,计算了四阱的光强分布,讨论了从光学四阱到双阱或单阱的演化过程,并导出了光学四阱的几何参量、光强分布、强度梯度及其曲率与光学透镜系统参量间的解析关系,获得了四阱间距与光栅空间频率的关系。研究表明通过改变余弦光栅的空间频率即可实现从光学四阱到双阱或单阱的连续双向演化。     

一种新颖的表面空心微光阱阵列

提出了采用四台阶相位光栅与微透镜阵列组合产生一种新颖的表面空心微光阱阵列的方案，研究了表面空心微光阱阵列的光强分布，计算了相应的光学囚禁势，并讨论了该微光阱阵列在原子分子光学中的潜在应用.研究表明当用1W的YAG激光照射时，在1cm²面积上可产生近10⁴个空心光阱，每个光阱具有较小的囚禁体积和较大的有效光强及其强度梯度，对⁸⁵Rb原子的光学囚禁势可达190μK.如此深的光阱足以囚禁冷原子或冷分子，并可用于实现全光型原子或分子玻色-爱因斯坦凝聚，甚至制备新颖的光学晶格等. 关键词： 空心光阱 冷原子或冷分子 光学晶格     

2D dark optical surface lattice with an efficient intensity-gradient cooling of atoms by evanescent wave interference

We propose a novel scheme to form a 2D dark optical surface lattice (DOSL) for cold atoms on the surface of the dense flint glass by using two sets of blue-detuned evanescent wave interference fields and a blue-detuned evanescent wave field. In the 2D DOSL, cold atoms will be trapped in the vicinity of minimum intensity and suffered the minimal light shift as well as the lowest coherence loss. The total potential and trap-depth of the individual optical micro-trap in the 2D DOSL are high enough to trap cold atoms (T = 120 μK) released from the standard magneto-optical trap (MOT), and atoms trapped in the 2D DOSL can be cooled to several μK with the efficient intensity-gradient Sisyphus cooling. The lattice constant of the DOSL can be controllable by changing the incident angles of lights.     

Nanoscale guiding for cold atoms based on surface plasmons along the tips of metallic wedges

We propose a novel scheme to guide neutral cold atoms in a nanoscale region based on surface plasmons (SPs) of one pair and two pairs of tips of metallic wedges with locally enhanced light intensity and sub-optical wavelength resolution. We analyze the near-field intensity distribution of the tip of the metallic wedge by the FDTD method, and study the total intensity as well as the total potential of optical potentials and van der Waals potentials for 87 Rb atoms in the light field of one pair and two pairs of tips of metallic wedges. It shows that the total potentials of one pair and two pairs of tips of metallic wedges can generate a gravito-optical trap and a dark closed trap for nanoscale guiding of neutral cold atoms. Guided atoms can be cooled with efficient intensity-gradient Sisyphus cooling by blue-detuned light field. This provides an important step towards the generation of hybrid systems consisting of isolated atoms and solid devices.     

实现冷原子、冷分子光学囚禁的组合三光学势阱方案

提出了一种利用单束平面光波照明液晶空间光相位调制器与透镜组合系统实现在透镜焦平面上的可演化组合三光学势阱方案.分析了该组合三光学势阱的形成原理,计算了势阱的相关特征参数,研究了从组合三光学势阱到双阱或到单阱的双向演化过程.最后,探讨了该组合三光学势阱及其新颖三阱光学晶格方案在实现物质波四波混频、三原子样品冷碰撞性质研究等领域中潜在应用前景. 关键词： 原子光学 原子分子囚禁 液晶空间光相位调制器 组合三光学势阱     

Controllable optical multi-well trap and its optical lattices using compounded cosine patterns

This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens illuminated by a plane light wave or a Gaussian beam.Dynamic manipulation and evolution of multi-well trap can be easily implemented by controlling the modulation frequency of the cosine patterns.It also discusses how to expand this multi-well trap to two-dimensional lattices with single-or multi-well trap by using an orthogonally or non-orthogonally modulated grating,as well as using incoherent multi-beam illumination,and these results show that all the symmetric structures of two-dimensional Bravais lattices can be obtained facilely by using proposed scheme.     

Observation of collective friction forces due to spatial self-organization of atoms: from Rayleigh to Bragg scattering

We demonstrate that emission-induced self-organization of two-level atoms can effect strong damping of the sample's center-of-mass motion. When illuminated by far-detuned light, cold cesium atoms assemble into a density grating that efficiently diffracts the incident light into an optical resonator. We observe random phase jumps of pi in the emitted light, confirming spontaneous symmetry breaking in the atomic self-organization. The Bragg diffraction results in a collective friction force with center-of-mass deceleration up to 1000 m/s(2) that is effective even for an open atomic transition.     

可操控二种冷原子或冷分子样品的光学双阱新方案及其实验研究

提出了一种构建可囚禁与操控二种冷原子或冷分子样品的光学双阱的新方案,该方案采用常用的液晶空间光调制器作为分光器件,分光调制函数类似二元相位光栅;对提出的方案进行了模拟实验研究,并研究了从光学双阱到单阱的双向演化过程,该光学双阱的模拟实验结果表明与理论方案相符,双阱的操控性好,有利于二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. 关键词： 原子光学 原子分子囚禁 液晶空间光相位调制器 光学双阱     

一种实现冷原子(或冷分子)囚禁的可控制纵向光学双阱

提出了一种新颖的实现冷原子(或冷分子)囚禁的可控制纵向光学双阱方案，它由一个二元π相位板及一会聚透镜所组成，其π相位板由两个面积相等的具有0和π相位的同心圆环组成. 当一平面光波通过此光学系统时将在光轴上透镜焦点两侧形成一个光学双阱，如果调节入射到二元π相位板上光束横截面的半径大小，即可实现从光学双阱到单阱的连续演变，或由单阱到双阱的连续变化. 介绍了本方案产生可控制光学双阱的基本原理，给出了形成光学双阱的最佳几何参数，研究了双阱、单阱及其演化过程的光阱参数、光强分布等与光学系统参数间的关系. 该方案不仅可用于双样品原子(分子)的光学囚禁及其全光型玻色-爱因斯坦凝聚(BEC)的实现，而且可用于研究超冷原子(或分子)物质波的干涉，或构成双层2D光阱列阵，甚至用于制备新颖的双层2D光学晶格. 关键词： 二元π相位板 可控制光学双阱 双样品囚禁 光学晶格     

Photonic nanojets as three-dimensional optical atom traps: A theoretical study

We show that an efficient three-dimensional optical atom trap can be achieved by light scattered off a dielectric microsphere. Namely, under suitable conditions, a plane wave incident on a polymer sphere produces a focal point in the forward scattering direction known as photonic nanojet. The photonic nanojet is formed at a distance of a few micrometers away from the surface of the sphere wherein the Casimir–Polder interaction felt by an atom is negligible compared to the optical and gravitational potentials. When many polymer spheres are brought together so as to form a linear chain, a one-dimensional periodic optical lattice filled with cold atoms is possible since interference between the incident and scattered beams is minimal when the spheres are not too close.     

用液晶空间光调制器产生光阱阵列

液晶空间光调制器能够方便地用于制作各种衍射型光学元件, 但液晶空间光调制器存在分辨率有限的缺点, 本文提出了用液晶空间光调制器制作相位型光栅, 产生一维和二维光阱阵列的新方案, 用迭代傅里叶级数算法优化设计光栅的相位分布, 在不改变空间光调制器硬件参数设置的情况下, 充分利用和发掘了空间光调制器的优点, 同时又能较好地回避其所存在的缺陷. 根据现有的空间光调制器的技术参数, 模拟仿真设计光栅, 计算光强分布, 结果表明: 用大失谐、小功率激光照明, 能够产生具有很高峰值光强和光强梯度的光阱阵列, 囚禁冷原子的光学偶极势达到mK量级, 对原子的作用力远大于原子的重力.     

Cavity enhanced measurement of trap frequency in an optical dipole trap

We demonstrate a direct, fluorescence-free measurement of the oscillation frequency of cold atoms in an optical dipole trap based on a high-finesse optical cavity strongly coupled to atoms. The parametric heating spectra of the trapped atoms are obtained by recording the transmitted photons from the cavity with the trap depth is modulated by different frequency.Moreover, in our method the oscillation can be observed directly in the time scale. Being compared to the conventional fluorescence-dependent method, our approach avoids uncertainties associated with the illuminating light and auxiliary imaging optics. This method has the potential application of determining the motion of atoms with stored quantum bits or degenerate gases without destroying them.     

通过圆孔衍射实现冷分子(或冷原子)囚禁的光学偶极阱

以单色标量波衍射理论为基础,研究单色平面波由圆孔衍射产生实现冷分子(或冷原子)光学囚禁的光阱。运用圆孔衍射理论分析讨论了光学偶极阱的光强分布、光学势及偶极力,并导出了有关光阱的几何参量、光强分布、强度梯度及其曲率与光学系统参量(如照明光波的波长、小孔的孔径)间的解析关系。研究表明,当激光功率与波长分别为P=500 W和λ=1.08μm,小孔半径a=20μm时,产生囚禁甲烷CH4分子的光阱光学势约为57.9μK。通过圆孔衍射可实现冷分子或冷原子囚禁,该方案不仅简单可行、操作方便,而且在冷分子物理、原子光学、分子光学和量子光学等领域中有着广阔的应用前景。     

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     

采用消逝波干涉的二维表面微光阱阵列

提出了一种采用两套超大红失谐消逝波干涉和一束蓝失谐消逝波光场来实现原子二维表面微光阱阵列和原子有效强度梯度冷却的新方案,得到了二维表面微光阱阵列的光强分布和光学势分布.研究发现,二维表面微光阱阵列中微光阱的光学势能够有效地囚禁从标准磁光阱中释放的冷原子,并且被囚禁的冷原子能在蓝失谐消逝波光场的作用下产生有效的强度梯度Sisyphus冷却,对⁸⁷Rb原子而言,原子温度能被冷却到2.56μK.该方案在冷原子物理、原子光学和量子光学领域中有着广阔的应用前景. 关键词： 消逝波干涉 微光阱阵列 原子囚禁 强度梯度冷却     

Diffracted field distribution from a knife-edge truncated semi-Gaussian beam as an atomic （molecular） mirror

We investigate the diffraction characteristics of an incident Gaussian beam cut by a straight edge bounding a semi-infinite opaque plane using Kirchhoff scalar wave theory in the Fresnel limit, and propose a new and simple mirror scheme to reflect atoms by using the intensity gradient induced by a blue-detuned semi-Gaussian laser beam. The optical potential of the diffracted light of the knife-cut semi-Gaussian beam for $^{85}$Rb atom and its spontaneous emission probability are calculated and compared with the performance of the evanescent-wave mirror. Our study shows that the optical potential of the diffracted light of the semi-Gaussian beam is far higher than that of the evanescent light wave, and the maximum normal velocity of the incident atoms can be far greater than that of the evanescent light wave under the same parameters, so the blue-detuned semi-Gaussian beam, as a novel atomic mirror, can be used to efficiently reflect cold atoms with a normal velocity of greater than 1 m/s. However, the intensity gradient (force) of the diffracted light of the semi-Gaussian-beam is much smaller than that of the evanescent light wave, so its spontaneous emission probability is greater than that from the evanescent-wave when the normal velocity of incident atoms is greater.     

Pulsed polarization gradient cooling in an optical dipole trap with a Laguerre-Gaussian laser beam

We utilized a blue-detuned Laguerre-Gaussian (doughnut) laser beam to trap cold rubidium atoms by optical dipole force. ”Pulsed” polarization gradient cooling was applied to the trapped atoms to suppress the trap loss due to heating caused by random photon scattering of the trapping light. In this trap about 10⁸ atoms were initially captured and the trap lifetime was 1.5 s, which was consistent with losses due to background gas collisions. This trap can readily be applied to atom guiding, compression, and evaporative cooling. Received: 10 July 1997 / Received in final form: 5 January 1998 / Accepted: 16 January 1998     

空间高层大气遥感远紫外成像光谱仪的光学系统

空间高层大气遥感远紫外成像光谱仪主要用于观测高层大气中的远紫外辐射和实现对其内部中尺度现象成像的功能。目前我国该类的相关仪器研究基础还比较薄弱,针对这种情况,在光学系统设计的角度上给出了一种适用于130～180nm波段探测的光学系统方案。该成像光谱仪光学系统以离轴抛物镜为物镜,串联Wadsworth结构为成像光谱系统;这种串联Wadsworth成像光谱系统采用离轴抛物镜做准直镜,分光器件为平面光栅和球面光栅串联,实现二次色散,同时球面光栅起到聚焦成像作用;在像差理论的基础上,对该结构的光程函数和各像差进行了分析,获得了改进结构的宽波段完善成像条件。针对低轨空间探测应用要求设计了相关改进型Wadsworth结构成像光谱仪光学系统,设计结果证明系统像差得到了充分校正,在奈奎斯特频率(20lp/mm)下全视场全波段调制传递函数值在0.6以上。该优化结构同时具备高空间分辨率和高光谱分辨率,性能优越。     

Long distance magnetic conveyor for precise positioning of ultracold atoms

We describe a chip-based magnetic conveyor that transports ultracold atoms with high positioning accuracy over long distances, into an interaction region which is well separated from the magneto-optical trap and gives good optical access to the atoms. The conveyor can work in two different modes, with or without external bias field. The transport potential is generated by a two-layer conductor pattern, enabling a significantly smoother transport than our earlier single-layer conveyor. This is confirmed by numerical field calculations, using an optimization procedure that minimizes shape deformations as well as deviations from the linear transport path. We experimentally demonstrate the use of this conveyor in the mode with external bias field, transporting a cloud of cold atoms over a linear distance of 6 cm and a total distance of 24 cm. We also describe an on-chip quadrupole trap that can be rotated by π/2. This trap is used to remove design constraints on the orientation of the laser beams in the surface magneto-optical trap. The long-distance conveyor is a versatile tool for experiments with trapped cold atoms, and can achieve sub-micrometric positioning precision. Possible applications of this tool are discussed.     

一种新颖的实现冷原子囚禁的可控制光学六阱及其光学晶格

提出了一种利用单束平面光波照明二元π相位板与透镜组合系统实现冷原子或冷分子囚禁的可控制光学六阱的方案,计算与分析了该方案产生的光学势阱的光强分布和光学六阱的特征参数、强度梯度及其曲率,讨论了从光学六阱到双阱或到单阱的演化过程,研究表明通过改变二元π相位板上的相位分布,即可实现光学六阱到双阱或到单阱的连续双向演化.