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This paper reports that two identical external-cavity-diode-laser (ECDL) based spectrometers are constructed at 634 nm referencing on the hyperfine B?X transition R(80)8?4 of 127I2. The lasers are stabilized on the Doppler-free absorption signals using the third-harmonic detection technique. The instability of the stabilized laser is measured to be 2.8 ? 10?12 (after 1000 s) by counting the beat note between the two lasers. The absolute optical frequency of the transition is, for the first time, determined to be 472851936189.5 kHz by using an optical frequency comb referenced on the microwave caesium atomic clock. The uncertainty of the measurement is less than 4.9 kHz.

We present an experimental study on the continuous atom laser. The experiments show that a high field seeking state atom laser with stable flux can be formed by increasing the strength of outcoupling before large density fluctuations appear. It is easy to obtain a long length or high speed output with this kind of atom laser.

The asymmetric patterns of superradiance from Bose–Einstein condensates are studied for the spatially inhomogeneous pump pulse with the semiclassical Maxwell-Schrodinger equations. The coupling dynamics between the optical field and condensate in the strong pulse and a faded wing in the weak coupling regime are discussed, which not only explain the spatial effects in the process of superradiance, but also supply a new method to control its patterns.

We investigate the magic wavelengths of the trapping laser for 6S1/2 – 6P3/2 of the Cs atom in a region where the optical shift between two different states can be eliminated. For fine levels and linear polarized laser they are 930.4 nm and 937.2 nm. The magic wavelengths range from 927.7 nm to 945.0 nm for circle-polarized perturbing laser. Effects of nuclear spin, the hyper-fine Zeeman levels, and the polarization of the light, which generate different magic wavelengths, are further discussed.

In this paper, We demonstrate an approach to determine the phase transition point and critical temperature of Bose-Einstein condensation. During the fitting sequence of time-of-flight images, for just one picture we take four kinds of different calculations instead of only one. By calculating the quantitative least-square errors, which have always been neglected before, we find out that this value can act as a criterion to judge the status of atom clouds. Using this criterion, we can not only discriminate the status around the phase transition point, but can also find the critical point precisely. Also with this method, we can achieve the totally automatical running of calculating programs without human's judgments.

Multiple-component Bose-Einstein condensation has been observed in a magnetic field generated by a controllable magnetic quadrupole-Ioffe-configuration trap. Different distributions of atoms in spinor Bose–Einstein condensates are created by changing the time difference of switching-off current in quadrupole-Ioffe-configuration coils and bias coils of the magnetic trap. A simple analysis is carried out to explain some phenomena of the experiment.

We study the energy eigenvalue and the yrast states for a harmonically two-component weak-interacting Bose–Einstein condensate (BEC) when the intra-species and interspecies scattering length are different. The energy shift for different energy eigenvalues related to intra- and interspecies scattering lengths is calculated with the perturbation method. The actual yrast spectrum is more complicated than that when intra-species and interspecies scattering length are equal. The degenerated features disappear and so do the perfect symmetric features.

The achievement of Bose–Einstein condensation (BEC) in our experiment is reported. The process of BEC formation is observed by detecting the image after free expansion, in which the effectiveness of runaway evaporative cooling is shown by measuring the optical density of the atom cloud. About 2×105 87Rb atoms in the |F = 2,mF = 2 state are condensed into the condensate. The ratio of axial-to-radial size of the condensate released from the magnetic trap is investigated in theory and experiment.

The magnetic quadrupole-Ioffe configuration (QUIC) trap in our Bose–Einstein condensation experiment is introduced. The magnetic trap loading process after laser cooling is analysed and the optimization of the loading process is studied experimentally. Calculation of the magnetic field explains the loss of the atoms during the loading process of the QUIC trap. The number of atoms loaded in the QUIC trap is increased by 40% after optimization in comparison with the normal loading process.

The coherent characteristics of four trapped Bose-Einstein condensates (BEC) conjunct one by one in a ring shape which is divided by two far off-resonant lasers, are studied. Four coupled Gross-Pitaevskii equations are used to describe the dynamics of the system. Two kinds of self-trapping effects are discussed in the coupled BECs, and the phase diagrams for different initial conditions and different coupling strengths are discussed. This study can be used to determine interaction parameters between atoms in BEC.

We first propose to study the phase of Bose-Einstein condensate in the phase space. The mean value of the phase and the phase fluctuation of Bose-Einstein condensate are considered, and their explicit expressions are given with the Thomas-Fermi approximation. For a finite atom number, we find that the phase of condensate is determined by the oscillation frequency of the harmonic confining potential at certain time. The effects of the atom number and time on the phase of condensate are also discussed for the same kinds of atoms.

We present an expression of the relative phase for two interacting Bose-Einstein condensates released from an isotropic trapping potential. We discuss the interference condition between condensates and the visibility of the interference pattern reflecting the interaction between the condensates.

Superradiant Rayleigh scattering in a Bose gas released from an optical lattice is analyzed with incident light pumping at the Bragg angle for resonant light diffraction. We show competition between superradiance scattering into the Bragg mode and into end-fire modes clearly leads to suppression of the latter at even relatively low lattice depths. A quantum light-matter interaction model is proposed for qualitatively explaining this result., 6 pages, 6 figures, accepted by PRA

We study superradiant scattering from a Bose-Einstein condensate using a pump laser incident at variable angle and show the presence of asymmetrically populated scattering modes. Experimental data reveal that the direction of the pump laser plays a significant role in the formation of this asymmetry, a result which is in good agreement with numerical simulations based on coupled Maxwell-Schroedinger equations. Our study complements the gap of previous work in which the pump laser was applied only along the short axis or the long axis of a condensate, and extends our knowledge about cooperative scattering processes.

An empirical formula, which demonstrates the interference fringe visibility as a function of the slit separation and the temperature of thermal atoms, is obtained by analysing a recent experiment [Bloch et al. Nature 403 (2000) 166] that refers to the spatial correlation function of a trapped Bose gas below the critical temperature. We find that the decay rate of the coherence function for the non-condensed component is about two orders larger than that of the pure condensed component. The changes of the interference fringe visibility versus the falling time for different temperatures and slit separations are also discussed.

We propose a scheme for realizing the long-term continuous output of an atom laser. In this scheme the cold atoms in several subsidiary Bose-Einstein condensates (BEC) will be coupled one by one in turn into one main BEC which serves for the continuous output of a coherent atomic beam. We discuss the process of the phase unification of the newly entered BEC atoms with the remaining atoms in the main BEC trap. An ideal dynamical equilibrium can be established when the transition rate of the uncondensed atoms transforming into the condensate and the decay rate of coupling output satisfy some conditions. The coupling method from the subsidiary BEC to the main BEC and the time rates of all different processes are considered.

We demonstrate a method to precisely calibrate the relative position between an optical dipole trap and a magnetic quadrupole potential in making a Bose-Einstein condensate via the hybrid trap. We measure the displacement by the dipole oscillation in the gravity direction, where the oscillation frequency can be adjusted through an additional bias magnetic field. One frequency corresponds to the case of the mode matching while two frequencies are not, and the great consistency between theoretical simulation and experimental results indicates its usefulness.

We present a 397-nm frequency-doubling system with a quasi-phase-matched KTP crystal (PPKTP) which features tunable, narrow linewidth, high power, and excellent mechanical stability. Using 20-mm and 30-mm-long PPKTP crystals, we establish two experimental setups based on different external cavity parameters. By testing the beat signal of these two lasers, the linewidth for the system is measured to be less than 2.5 MHz. The maximum power of blue light can be achieved up to 40 mW. With these performance characteristics, the constructed blue laser system is useful for applications in cold atom physics and precision measurements.

In the frame of quantum mechanics, we consider an ensemble of spin-½ neutral particles passing through a Stern–Gerlach apparatus and explore how their motions depend on the initial phase difference between two internal spin states. Assuming the particles moving along y-axis, due to the initial phase difference between spin states, they not only split along the longitudinal direction (z-axis) but also separate along the lateral direction (x-axis). The dependence of the lateral displacement on the initial phase difference reminds one of the picture of a quantum interference. This generalized interference provides an alternative approach to measuring the initial phase difference. The experimental realization with ultracold atoms or Bose–Einstein condensates is also discussed.

A scheme for a microwave atomic clock is proposed for Cs or Rb atoms trapped in a blue detuned optical lattice. The ac Stark shift of the clock transition due to a trapping laser is calculated. We analyze it at some specific laser wavelength. Compared with the case of the fountain clock, the cavity related shifts, the collision shift and the Doppler effect are eliminated or suppressed dramatically in an atomic lattice clock. By analyzing various sources of clock uncertainty, a microwave atomic lattice clock with a high accuracy and small volume is feasible.

We construct an ultra-stable external-cavity diode laser via modulation transfer spectroscopy referencing on a hyperfine component of the 87Rb D2 lines at 780nm. The Doppler-free dispersion-like modulation transfer signal is obtained with high signal-to-noise-ratio. The instability of the laser frequency is measured by beating with an optical frequency comb which is phase-locked to an ultra-stable oven controlled crystal oscillator. The Allan deviation is 3.9 × 10−13 at 1s averaging time and 9.8 × 10−14 at 90s averaging time.