共查询到20条相似文献,搜索用时 500 毫秒
1.
Aranya B. Bhattacherjee 《Optics Communications》2009,282(17):3641-948
We investigate the interaction between a single mode light field and an elongated cigar shaped Bose-Einstein condensate (BEC), subject to a temporal modulation of the trap frequency in the tight confinement direction. Under appropriate conditions, the longitudinal sound like waves (Faraday waves) in the direction of weak confinement acts as a dynamic diffraction grating for the incident light field analogous to the acousto-optic effect in classical optics. The change in the refractive index due to the periodic modulation of the BEC density is responsible for the acousto-optic effect. The dynamics is characterised by Bragg scattering of light from the matter wave Faraday grating and simultaneous Bragg scattering of the condensate atoms from the optical grating formed due to the interference between the incident light and the diffracted light fields. Varying the intensity of the incident laser beam we observe the transition from the acousto-optic effect regime to the atomic Bragg scattering regime, where Rabi oscillations between two momentum levels of the atoms are observed. We show that the acousto-optic effect is reduced as the atomic interaction is increased. 相似文献
2.
We transfer cold ^87 Rb atoms from a vapour cell chamber to a spatially separated UHV magneto-optical trap (MOT) with the assistance of a red-detuned optical guiding beam and a normal push beam. Efficient optical guiding of the cold atoms is observed within a small detuning window. A pulsed optical guiding beam enhances the transfer efficiency and hence allows us to collect more atoms in UHV MOT in a shorter time, which is favourable for our experiment of achieving Bose-Einstein condensates (BEC). Besides the easy operation, another advantage of this optical guiding technique is also demonstrated such that slower atomic beams may be efficiently transferred along horizontal direction. This study is a direct application of the optical guiding technique as a powerful tool. 相似文献
3.
In this paper, the squeezing properties of the probe light field in the process preparing Raman-type atom laser via stimulated Raman transition of the sodium atom Bose-Einstein condensate (BEC) interacting with two light beam of a weaker squeezed coherent probe light and a stronger classical pump light are studied. The results show that the probe light can be periodically squeezed. The squeezing period is related to the mean number of atoms in trap, the strength of interaction between squeezed light and BEC atoms, and the detuning of the light, and the squeezing depth is determined by the initial squeezing factor of the probe light. 相似文献
4.
5.
We report suppression of atomic heating by light scattering due to tight binding in a 3D far-off-resonant optical lattice. We show that rescattered spontaneously emitted photons do not heat trapped atoms when the scattering rate is much less than the trap vibrational frequency. 相似文献
6.
We present a scheme to generate a squeezed atom laser via stimulated Raman transition of the atoms in Bose-Einstein condensate (BEC) interacting with two light beams, including a weaker squeezed coherent probe light and a stronger classical pump light. The results show that the quantum fluctuation of this atom laser can be periodically squeezed. The squeezing depth of such atom laser is determined by the initial squeezing factor of the probe light, and the squeezing period of that is related to the mean number of atoms in the trap, the strength of interaction between squeezing light and BEC atoms, and the detuning of the light. 相似文献
7.
We experimentally demonstrate the trapping of ^85Rb atoms directly on a chip-size U-shaped magneto-optical trap (U-MOT). The trap includes a U-shaped wire on the chip, two bias magnetic field coils and laser beams. The capture volume of the U-MOT is theoretically calculated, and the trap is experimentally realized. With 2 A current applied to the U-shaped wire and 2-Gauss horizontal bias field, more than 2 × 10^6 atoms are trapped. In contrast with an ordinary mirror-MOT, this U-MOT captures atoms directly from the background, thus the trap size is greatly reduced. Based on this mini trap scheme, it is possible to realize a chip-size atom trap array for quantum information processing. 相似文献
8.
Quantum Degenerate Fermi--Bose Mixtures of 40K and 87Rb Atoms in a Quadrupole-Ioffe Configuration Trap 总被引:2,自引:0,他引:2 下载免费PDF全文
We report on the attainment of quantum degeneracy of 40^K by means of efficient thermal collisions with the evaporatively cooled 87^Rb atoms. In a quadrupole-Ioffe configuration trap, potassium atoms axe cooled to 0.5 times the Fermi temperature. We obtain up to 7.59 × 10^5 degenerate fermions 40^K. 相似文献
9.
We report the experimental realization of a ^88Sr magneto-optical trap (MOT) operating at the wavelength of 461 nm. The MOT is loaded via a 32 cm long spin-flip type Zeeman slower which enhances the MOT population by a factor of 22. The total laser power available in our experiment is about 300mW. We have trapped 1.6 × 10^8 ^88 Sr atoms with a 679nm and 707nm repumping laser. The two repumping lasers enhance the trap population and trap lifetime by factors of 11 and 7, respectively. The ^88 Sr cloud has a temperature of about 2.3 mK, measured by recording the time evolution of the absorption signal. 相似文献
10.
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
11.
K.-P. Marzlin W. Zhang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):241-253
An extended Bose-Einstein condensate (BEC) in an optical lattice provides a kind of periodic dielectric and causes band gaps
to occur in the spectrum of light propagating through it. We examine the question whether these band gaps can modify the spontaneous
emission rate of atoms excited from the BEC, and whether they can lead to a self-stabilization of the BEC against spontaneous
emission. We find that self-stabilization is not possible for BECs with a density in the order of 1014 cm-3. However, the corresponding non-Markovian behavior produces significant effects in the decay of excited atoms even for a
homogeneous BEC interacting with a weak laser beam. These effects are caused by the occurrence of an avoided crossing in the
photon (or rather polariton) spectrum. We also predict a new channel for spontaneous decay which arises from an interference
between periodically excited atoms and periodic photon modes. This new channel should also occur in ordinary periodic dielectrics.
Received 27 March 2000 相似文献
12.
Boussen S. Hoang N. Guibal S. Zahzam N. Pruvost L. Marescaux D. Pinard J. Pillet P. 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,28(2):259-266
Bose-Einstein condensation (BEC) in a atomic cesium gas prepared in a low field seeker Zeeman sublevel and confined in a magnetic trap has been thwarted by a high cross-section of inelastic spin-flip collisions. A recent experiment [1] succeeded in reaching BEC for cesium atoms using all optical methods and tuning the scattering length. We will discuss a hybrid magnetic and optical trap for cesium atoms in the true hyperfine ground state, the high field seeker Zeeman sublevel, F = m
F
= 3. Although this trap allows only one-dimensional (1D) evaporative cooling, we show that a route towards BEC with such a trap should be possible. We present simulations of 1D evaporative cooling, which shows that a high phase space density (PSD) of 0.1 could be reached in less than 10 seconds.Received: 25 July 2003PACS:
03.75.Hh Static properties of condensates; thermodynamical, statistical and structural properties - 05.30.Jp Boson systems - 32.80.Pj Optical cooling of atoms; trappingLaboratoire Aimé Cotton is associated with University of Paris-Sud. 相似文献
13.
An elongated trap potential for cold atoms is designed based on a quadrupole-Ioffe configuration.Phase fluctuations in a Bose-Einstein condensate(BEC),which is confined by the trap,are studied.We simulate the atom density distribution induced by fluctuation after time of flight from this elongated trap potential and study the temperature measurement method related to the distribution.Furthermore,taking advantage of the tight confinement and radio frequency dressing technique,we propose a double well potential for splitting BECs.Our results are helpful for improving understanding of low-dimensional quantum gases and provide important guidance for atomic interferometry. 相似文献
14.
We develop a functional integral formalism for ultracold gases of fermionic atoms. It describes the BEC–BCS crossover and involves both atom and molecule fields. Beyond mean field theory we include the fluctuations of the molecule field by the solution of gap equations. In the BEC limit, we find that the low temperature behavior is described by a Bogoliubov theory for bosons. For a narrow Feshbach resonance these bosons can be associated with microscopic molecules. In contrast, for a broad resonance the interaction between the atoms is approximately pointlike and microscopic molecules are irrelevant. The bosons represent now correlated atom pairs or composite “dressed molecules”. The low temperature results agree with quantum Monte Carlo simulations. Our formalism can treat with general inhomogeneous situations in a trap. For not too strong inhomogeneities the detailed properties of the trap are not needed for the computation of the fluctuation effects—they enter only in the solutions of the field equations. 相似文献
15.
N. Veretenov Yu. Rozhdestvensky N. Rosanov V. Smirnov S. Fedorov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):455-460
We propose the precision measurement of both angular rotation and of the gradient magnetic of a field based on the use of
matter wave interferometers with soliton states of a Bose-Einstein condensate (BEC). We consider the formation of these soliton
states in a BEC with negative scattering length by an optical lattice produced by two counterpropagating laser beams. We determine
the parameters of both the initial condensate and the optical radiation necessary for the formation of coherent solitons.
We demonstrate
that this interferometer can be used to measure magnetic field gradient with a precision of 10-2 pT/cm. Our calculations show that the sensitivity of a gyroscope based on a ring, two-port matter wave interferometer can
achieve 2.6×10-7 rad s-1. The precision of this method is more than ten times greater than in that of rotating interferometer with cooled atoms. 相似文献
16.
Precision Calculations of Atomic Polarizabilities: A Relevant Physical Quantity in Modern Atomic Frequency Standard 下载免费PDF全文
Electric dipole polarizabilities of atoms are very important in many different physical applications, such as the precision atomic frequency standard. Calculations of these properties are very important and challenging. We propose a calculation strategy to calculate the frequency dependent dipole polarizabilities with high precision variationally by using a set of high quality orbital bases where the electron correlations can be taken into account adequately. The static polarizabilitiez of the ground state of Na are calculated accurately by such a method and can be compared with precision experiment measurement directly. The calculation result is in excellent agreement with the available experimental measurements within about 0.1~, which demonstrates the validity of our strategy. Our calculation strategy has a wide usage, not only in polarizibilies, but also in other fields such as theoretical treatment of electron-atom scattering processes. Using the same orbital bases, we carry out precision calculation of Na- affinities. Our calculated affinity is in excellent agreement with precision laser spectroscopy measurements within 0. 1%. 相似文献
17.
采用二维磁光阱产生了-个快速~(87)Rb原子流,并在高真空的三维磁光阱中实现了~(87)Rb原子的快速俘获,进一步采用射频蒸发冷却技术实现了原子云的预冷却,然后将原子转移到远失谐的光学偶极阱中蒸发得到了玻色-爱因斯坦凝聚体.实验上可以在25 s内完成三维磁光阱的装载(约1.0×10~(10)个~(87)Rb原子),然后经过16 s的冷却过程最终在光学偶极阱中获得5.0×10~5个原子的玻色-爱因斯坦凝聚体.实验重点研究了二维磁光阱的优化设计和采用蓝失谐大功率光束对四极磁阱零点的堵塞,抑制四极磁阱中原子的马约拉纳损耗,更加有效地对原子云进行预冷却. 相似文献
18.
Nonadiabatic effects on population transfer of two Bose-Einstein condensates induced by atomic interaction 下载免费PDF全文
We investigate the stimulated Raman adiabatic passage for Bose-Einstein condensate (BEC) states which are trapped in different potential wells or two ground states of BEC in the same trap. We consider that lasers are nearly resonant with the atomic transitions. The difference of population transfer processes between BEC atoms and usual atoms is that the atomic interaction of the BEC atoms can cause some nonadiabatic effects, which may degrade the process. But with suitable detunings of laser pulses, the effects can be remedied to some extent according to different atomic interactions. 相似文献
19.
We investigate the Landau damping of collective modes in an anisotropic Bose Einstein condensate (BEC), Based on divergence-free analytical solutions for the ground state wavefunction of the condensate and all eigenvalues and eigenfunctions for thermal excited quasiparticles, we make a detailed analytical calculation on coupling matrix elements. We evaluate the Landau damping of a quadrupole collective mode in the BEC with a disc-shaped trap and discuss its dependence on temperature and particle number of the system. 相似文献
20.
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