共查询到20条相似文献,搜索用时 15 毫秒
1.
We demonstrate the direct loading of cold atoms into a microchip 2-mm Z-trap, where the evaporative cooling can be performed efficiently, from a macroscopic quadrupole magnetic trap with a high loading efficiency. The macroscopic quadrupole magnetic trap potential is designed to be moveable by controlling the currents of the two pairs of anti-Helmholtz coils. The cold atoms are initially prepared in a standard six-beam magneto-optical trap and loaded into the macroscopic quadrupole magnetic trap, and then transported to the atom chip surface by moving the macroscopic trap potential. By means of a three-dimensional absorption imaging system, we are able to optimize the position alignment of the atom cloud in the macroscopic trap and the microchip Z-shaped wire. Consequently, with a proper magnetic transfer scheme, we load the cold atoms into the microchip Z-trap directly and efficiently. The loading efficiency is measured to be about 50%.This approach can be used to generate appropriate ultracold atoms sources, for example, for a magnetically guided atom interferometer based on atom chip. 相似文献
2.
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
3.
为了制备适于原子干涉仪实验的低温锂原子样品,开展了锂原子的塞曼减速及与磁光阱囚禁相关的实验研究.设计并实现了一种结构紧凑的腔体内冷式多级线圈叠加的塞曼减速器,将速度小于600 m/s的7Li原子减速到60 m/s,磁光阱装载速率为5×108/s,囚禁原子数目1×109个,原子团的最低温度约为220±30μK.研究了光学黏胶中7Li原子的寿命与囚禁光频率失谐量的关系.这些结果为进一步开展7Li原子亚多普勒冷却、光势阱蒸发冷却以及原子干涉仪实验奠定了基础. 相似文献
4.
A. di Stefano D. Wilkowski J.H. Müller E. Arimondo 《Applied physics. B, Lasers and optics》1999,69(4):263-268
We have operated a magneto-optical trap and optical molasses for the laser cooling of cesium atoms on the basis of a five-beam
laser configuration. For the magneto-optical trap two laser beams counterpropagate along the axis of a quadrupole trap and
the remaining three beams propagate in the orthogonal plane at 120° to each other. The same optical configuration was used
for the optical molasses. We have tested the efficiency in atom collection and the temperatures reached in both cooling processes.
In comparison to previous results on a six-beam configuration, a lower number of atoms is collected, while comparable densities
are realized. The atomic temperatures have been measured through a delayed shadow-image technique, where one of the running-wave
cooling beams produces an absorptive image of the atoms on a camera.
Received: 14 January 1999 / revised version: 23 June 1999 / Published online: 8 September 1999 相似文献
5.
6.
7.
Y. Torii N. Shiokawa T. Hirano T. Kuga Y. Shimizu H. Sasada 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(3):239-242
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 相似文献
8.
This paper presents an experimental demonstration of light-induced
evaporative cooling in a magneto-optical trap. An additional laser
is used to interact with atoms at the edge of the atomic cloud in
the trap. These atoms get an additional force and evaporated away
from the trap by both the magnetic field and laser fields. The
remaining atoms have lower kinetic energy and thus are cooled. It
reports the measurements on the temperature and atomic number after
the evaporative cooling with different parameters including the
distance between the laser and the centre of the atomic cloud, the
detuning, the intensity. The results show that the light-induced
evaporative cooling is a way to generate an ultra-cold atom source. 相似文献
9.
We report on a novel mechanism that allows for strong laser cooling of atoms that do not have a closed cycling transition. This mechanism is observed in a magneto-optical trap (MOT) for erbium, an atom with a very complex energy level structure with multiple pathways for optical-pumping losses. We observe surprisingly high trap populations of over 10(6) atoms and densities of over 10(11) atoms cm(-3), despite the many potential loss channels. A model based on recycling of metastable and ground state atoms held in the quadrupole magnetic field of the trap explains the high trap population, and agrees well with time-dependent measurements of MOT fluorescence. The demonstration of trapping of a rare-earth atom such as erbium opens a wide range of new possibilities for practical applications and fundamental studies with cold atoms. 相似文献
10.
We report on the creation of a two-dimensional Bose-Einstein condensate of cesium atoms in a gravito-optical surface trap. The condensate is produced a few microm above a dielectric surface on an evanescent-wave atom mirror. After evaporative cooling by all-optical means, expansion measurements for the tightly confined vertical motion show energies well below the vibrational energy quantum. The presence of a condensate is observed in two independent ways by a magnetically induced collapse at negative scattering length and by measurements of the horizontal expansion. 相似文献
11.
三维拉曼边带冷却后的铯原子样品装载于一个磁悬浮的大体积交叉光学偶极阱中, 继续加载一个小体积的光学偶极阱后, 实现了Dimple光学偶极阱对铯原子的高效装载. 对不同磁场下磁悬浮大体积光阱的有效装载势能进行理论分析与实验测量, 得出最优化的梯度磁场和均匀偏置磁场, 获得了基于磁悬浮大体积光阱的Dimple光学偶极阱的装载势能曲线, 实现了Dimple光学偶极阱对经拉曼边带冷却后俘获在磁悬浮的大体积光阱中的铯原子样品的有效装载. 比较了Dimple光学偶极阱分别从拉曼边带冷却、大体积的交叉光阱和消除反俘获势后的磁悬浮大体积光阱装载的结果, 将俘获在磁悬浮大体积光阱中的铯原子样品装载到Dimple光学偶极阱, 铯原子样品的密度提高了约15倍. 相似文献
12.
Individual laser-cooled atoms are delivered on demand from a single atom magneto-optic trap to a high-finesse optical cavity using an atom conveyor. Strong coupling of the atom with the cavity field allows simultaneous cooling and detection of individual atoms for time scales exceeding 15 s. The single atom scatter rate is studied as a function of probe-cavity detuning and probe Rabi frequency, and the experimental results are in qualitative agreement with theoretical predictions. We demonstrate the ability to manipulate the position of a single atom relative to the cavity mode with excellent control and reproducibility. 相似文献
13.
P. L. Chapovsky 《Journal of Experimental and Theoretical Physics》2006,103(5):711-719
Spectral characteristics of rubidium atoms confined in a dark magneto-optical trap (DMOT) are measured, including probe absorption spectra and atom density as a function of the cooling and repumping laser frequencies. The trap can capture and cool more than 2.5 × 108 rubidium atoms, confining them in a hyperfine state weakly perturbed by the laser beams used to form the trap. The optical density of the trapped atomic cloud approaches 9. A qualitative model of the DMOT operation is presented, based on the experimental results obtained. 相似文献
14.
Doppler cooling of 88Sr atoms is studied in the presence of off-resonant red-detuned fluctuating laser fields.Using a semi-classical approach,we show that the relevant physical quantities in the cooling process,such as optical forces,the damping coefficient,Doppler temperature,and atom number in the trap,are strongly affected by the laser amplitude and phase fluctuations.We find that the Doppler cooling limit is higher than the predicted Doppler theory for non-fluctuating lasers.This ... 相似文献
15.
We propose a new method of cooling and phase space compression that requires each atom to scatter only one photon. We consider the specific example of rubidium-87 atoms confined to a magnetic trap and provide realistic estimates. Beyond a demonstration in atomic rubidium, this method could enable cooling of atoms and molecules that do not have cycling transitions. 相似文献
16.
The dynamics of Bose-condensate generation by a cw atom laser with simultaneous stimulated evaporative cooling in a magnetic trap was analyzed using a quantum-mechanical master equation. The model of the atom laser includes irreversible processes of incoherent trap mode pumping and spontaneous atomic transitions due to the interaction of the atomic ensemble with heat reservoirs. The inelastic atomic collisions in the trap and the continual coherent Bose-condensate output coupling from the trap were considered. At certain values of parameters, the Bose condensate created in this laser scheme occurs in a compressed sub-Poisson state. For large Bose condensates with a mean number of atoms ~106, the Fano factor may be as high as ?0.5. The influence of spontaneous transitions from the excited trap modes on the statistics of Bose condensate was analyzed. 相似文献
17.
18.
T. David Y. Japha V. Dikovsky R. Salem C. Henkel R. Folman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(3):321-332
We analyze atom-surface magnetic interactions on atom chips where the magnetic trapping potentials are produced by current
carrying wires made of electrically anisotropic materials.
We discuss a theory for time dependent fluctuations of the magnetic potential, arising from thermal noise
originating from the surface. It is shown that using materials with a large electrical anisotropy results in a considerable
reduction of heating
and decoherence rates of ultra-cold atoms trapped near the surface, of up to several orders of magnitude. The trap
loss rate due to spin flips is expected to be significantly reduced
upon cooling the surface to low temperatures. In addition, the electrical anisotropy
significantly suppresses the amplitude of static spatial potential corrugations due to
current scattering within imperfect wires. Also the shape of the corrugation pattern depends on the electrical anisotropy:
the preferred angle of the scattered current wave fronts can be varied over a wide range. Materials, fabrication, and experimental
issues are discussed, and specific candidate materials are suggested. 相似文献
19.
We demonstrate an atom laser using all-optical techniques. A Bose-Einstein condensate of rubidium atoms is created by direct evaporative cooling in a quasistatic dipole trap realized with a single, tightly focused CO2-laser beam. An applied magnetic field gradient allows the formation of the condensate in a field-insensitive m(F)=0 spin projection only, which suppresses fluctuations of the chemical potential from stray magnetic fields. A collimated and monoenergetic beam of atoms is extracted from the Bose-Einstein condensate by continuously lowering the dipole trapping potential in a controlled way to form a novel type of atom laser. 相似文献