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1.
This paper reports an experiment of creating Bose-Einstein
condensate (BEC) on an atom chip. The chip-based Z-wire current with
a homogeneous bias magnetic field creates a tight magnetic trap,
which allows for a fast production of BEC. After a 4.17-s forced
radio frequency evaporative cooling, a condensate with about 3000
atoms appears. The transition temperature is about 300~nK. This
compact system is quite robust, allowing for versatile extensions
and further studying of BEC. 相似文献
2.
Chip-based atom interferometers bring together the
advantages of atom chips and Bose--Einstein condensates. Their central
prerequisite is that a condensate can be coherently split into two
halves with a determined relative phase. This paper demonstrates the
dynamical splitting and merging of an atom cloud with two U-wires on
an atom chip. Symmetrical and asymmetrical splittings are realized
by applying a bias field with dif\/ferent directions and
magnitudes. The trajectories of the splitting are consistent with
theoretical calculations. The atom chip is a good candidate for
constructing an atom interferometer. 相似文献
3.
We report an experimental demonstration of a new scheme to split cold atoms on an atom chip. The atom chip consists of a U-wire and a Z-wire. The cold atom cloud is initially loaded and prepared in the Z-trap, which is split into two separate parts by switching on the current of the U-wire. The two separate atom clouds have a distance more than one millimeter apart from each other and show almost symmetrical profiles, corresponding to about a 50/50 splitting ratio. 相似文献
4.
We have studied theoretically and numerically the enhanced cooling of a V-type three-level atom in a high-finesse optical cavity and shown that the cooling rate can be increased by one order of magnitude over that of a two-level atom, and the momentum amplitude tends to a stationary state much smaller than that of a two-level atom. We have further shown that the cooling rate can be significantly improved by using feedback and a time-dependent pump. 相似文献
5.
The effects of surface-induced evaporative cooling on an atom chip
are investigated. The evolutions of temperature, number and
phase-space density of the atom cloud are measured when the atom
cloud is brought close to the surface. Rapid decrease of the
temperature and number of the atoms is found when the atom-surface
distance is < 100~μm. A gain of about a factor of five on the
phase-space density is obtained. It is found that the efficiency
of the surface-induced evaporative cooling depends on the
atom-surface distance and the shape of the evaporative trap. When
the atoms are moved very close to the surface, severe heating is
observed, which dominates when the holding time is >8~ms. It is
important that the surface-induced evaporative cooling offers novel
possibilities for the realization of a continuous condensation,
where a spatially varying evaporative cooling is required. 相似文献
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7.
Truscott A. G. Heckenberg N. R. Rubinsztein-Dunlop H. 《Optical and Quantum Electronics》1999,31(5-7):417-430
The free running linewidth of an external cavity grating feedback diode laser is on the order of a few megahertz and is limited by the mechanical and acoustic vibrations of the external cavity. Such frequency fluctuations can be removed by electronic feedback. We present a hybrid stabilisation technique that uses both a Fabry–Perot confocal cavity and an atomic resonance to achieve excellent short and long term frequency stability. The system has been shown to reduce the laser linewidth of an external cavity diode laser by an order of magnitude to 140 kHz, while limiting frequency excursions to 60 kHz relative to an absolute reference over periods of several hours. The scheme also presents a simple way to frequency offset two lasers many gigahertz apart which should find a use in atom cooling experiments, where hyperfine ground-state frequency separations are often required. 相似文献
8.
<正>We propose a wire configuration to create a one-dimensional(1D) array of magnetic microtraps for trapping ultracold atoms.The configuration is formed by replacing the central part of the Z-wire pattern with a zigzag wire. We simulate the performance of this pattern by the finite element method which can take both the width and depth of the wire into consideration.The result of simulation shows that this configuration can create magnetic microtraps which can be separated and combined by changing the bias magnetic field.We manage to split the Z-wire trap and prove that a similar result can occur for the new wire configuration.The fabrication processes of the atom chip are also introduced.Finally we discuss the loading method. 相似文献
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10.
高强度的亚稳态惰性原子束流在原子分子物理实验研究中具有广泛的应用.使用射频电离方法和激光横向冷却技术制备了高强度的亚稳态氪原子束流,并使用数值模拟方法对横向冷却激光场中的原子径迹进行了分析.通过激光诱导荧光光谱方法测量原子束的束流特性,结果显示,横向冷却后在束流源下游230 cm处的原子束流强度达1.6atoms/(s*sr),束流强度提高了两个量级.利用这种高强度原子束流,我们成功囚禁了1.3×1010个亚稳态84Kr原子,同时冷原子装载速率达到了3.0×1011atoms/s;并利用该装置成功地实现了高亮度的亚稳态氩原子束和原子阱.
关键词:
横向冷却
原子束
原子阱
惰性气体 相似文献
11.
We demonstrated two experimental methods of producing and
guiding pulsed atomic beams on chip. One is to trap atoms first in a
U-type magneto-optical trap on the chip, then transfer them to the
magnetic guide field and push them simultaneously by a continuous
force from the power imbalance of the magneto-optical trap laser
beams hence the pulsed cold atom beams are produced and move along
the magnetic guide to the destination. The other is to trap atoms
directly by a H-type magneto-optical trap, then push them to make
them move along the magnetic guide field, thus high rate cold atom
beams can be produced and guided on the chip. 相似文献
12.
Radiation pressure and laser cooling of a three-level atom in a ladder configuration 总被引:1,自引:0,他引:1 下载免费PDF全文
Radiation pressure and laser cooling of a moving three-level ladder-type atom in bichromatic travelling fields are considered. The dependence of the force on parameters such as detunings, Rabi frequencies and spontaneous decay rates is calculated numerically and shown graphically, and analytical expressions for the force are obtained for some special parameter values. It is shown that the radiation pressure shows Doppler-shifted resonance peaks resulting respectively from one-photon and two-photon transitions. Using the present scheme, Doppler cooling of sodium exploiting the 3{}^2S_{1/2}-3{}^2P_{3/2}-3{}^2D_{5/2} cascade transitions is investigated. It is found that temperatures lower than the Doppler limit can be achieved. 相似文献
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《Physics letters. A》2014,378(30-31):2034-2037
A novel method of angled incidence for diffuse laser cooling of 87Rb is presented to improve the distribution of cold atom density in an integrating sphere. The angled injection scheme could cool more atoms in the middle of the sphere compared to the previous normal injection scheme. The loading time of the cold atoms for the angled injection scheme is twice as that of the normal injection scheme. The SNR and the contrast of the detected signal would be improved in the angled injection scheme. 相似文献
18.
V. B. Tiwari S. R. Mishra H. S. Rawat S. Singh S. P. Ram S. C. Mehendale 《Pramana》2005,65(3):403-411
We present results of a study of frequency stabilization of a diode laser (λ = 780 nm) using the Doppler-free dichroic lock
(DFDL) technique and its use for laser cooling of atoms. Quantitative measurements of frequency stability were performed and
the Allan variance was found to be 6.9 × 1011 for an averaging time of 10 s. The frequency-stabilized diode laser was used to obtain the trapping beams for a magneto-optic
trap (MOT) for Rb atoms. Using the DFDL technique, the laser frequency could be locked over a wide range and this enabled
measurement of detuning dependence of the number and temperature of cold atoms using a relatively simple experimental set-up. 相似文献
19.
提出了一种采用单模光纤、环形二元相位板和微透镜组成的光束整形系统产生亚微米局域空心光束的方案. 根据瑞利-索莫菲衍射积分公式, 数值计算了微透镜焦平面附近的场分布, 详细研究了空心光束的暗斑尺寸与单模光纤模场半径和微透镜焦距的关系. 数值计算结果表明: 在微透镜焦平面附近光场分布近似对称, 在焦点处场强近似为零, 周围场强逐渐增大, 形成半径约为0.4 μm的三维封闭的球形空心光场区域, 即亚微米局域空心光束. 当局域空心光束为蓝失谐时, 光场中的原子将被囚禁在光场最弱处. 若加上抽运光, 原子将受到蓝失谐局域空心光束与抽运光共同激发的强度梯度Sisyphus冷却. 本文利用该方案产生的亚微米局域空心光束构建单原子的囚禁与冷却器件, 并以单个87Rb原子为例, 利用Mont-Carlo方法研究亚微米局域空心光束中单原子囚禁与强度梯度冷却的动力学过程, 结果表明利用该器件可以获得温度在5.8 μK量级的超冷单原子. 相似文献
20.
Atom probe tomography (APT) combined with electron back scatter diffraction and transmission electronic microscopy (TEM) is utilized to characterize the nature of copper precipitation during austenite–ferrite transformation in a continuous cooling high-strength low-alloy steel. The copper precipitation manners in association with the austenite decomposition kinetics are studied. The prevailing microstructure of the continuous cooling steel consists of acicular ferrite (AF), which is formed at an intermediate cooling rate of 10?°C/s. Besides, a limited volume of polygonal ferrite (PF) because of fast cooling rate and a trace of retained austenite are detected. Numerous copper-rich phase is found by TEM observation both in highly dislocated AF and dislocation-free PF. Generally, the copper-rich precipitates have comparatively large sizes and are considered to be formed by interphase precipitation during austenite–ferrite transformation. A high number density of nanometre sized copper-rich clusters that are lack of diffraction contrast in conventional TEM observation are detected by APT. These smaller copper-rich clusters, which are usually located between the linear-arranged copper-rich precipitates, are considered to be formed from supersaturated solid solution after the cessation of austenite–ferrite transformation. That means an ageing reaction for Cu precipitation occurs during continuous cooling transformation. The copper-rich precipitates and clusters are both rich in nickel, manganese and iron. 相似文献