Trapping of neutral atoms with a radio-frequency field

Based on the dressed-atom approach, we discuss a two-dimensional (2D) radio-frequency trap for neutral atoms, in which the trap potential derives from the magnetic-dipole transition among the hyperfine Zeeman sublevels. By adjusting the detuning of the radiation from resonance, the trapping states will be changed predominantly from the bare states Of m(FgF) > 0 to other states of m(FgF) < 0, where m(F) and g(F) are the quantum numbers of Zeeman sublevels and the Lande factor, respectively. This character contrasts finely with that, of a static magnetic, trap that can only trap or guide the states of m(FgF) > 0. In comparison to the optical field, the radio-frequency trap eliminates the spontaneous emission heating of the atoms. Unlike other oscillating traps reported in the e literature, the configuration of the radio-frequency trap is suitable for realization of a miniature magnetic guide.

Energy spectrum of two-component Bose-Einstein condensates in optical lattices

With the method of Green's function, we investigate the energy spectra of two-component ultracold bosonic atoms in optical lattices. We End that there are two energy bands for each component. The critical condition of the superfluid-Mott insulator phase transition is determined by the energy band structure. We also find that the nearest neighboring and on-site interactions fail to change the structure of energy bands, but shift the energy bands only. According to the conditions of the phase transitions, three stable superfluid and Mott insulating phases can be found by adjusting the experiment parameters. We also discuss the possibility of observing these new phases and their transitions in further experiments.

Energy spectrum of ground state and excitation spectrum of quasi-particle for hard-core boson in optical lattices

We investigate the energy spectrum of ground state and quasi-particle excitation spectrum of hard-core bosons, which behave very much like spinless noninteracting fermions, in optical lattices by means of the perturbation expansion and Bogoliubov approach. The results show that the energy spectrum has a single band structure, and the energy is lower near zero momentum; the excitation spectrum gives corresponding energy gap, and the system is in Mott-insulating state at Tonks limit. The analytic result of energy spectrum is in good agreement with that calculated in terms of Green's function at strong correlation limit.

Effects of PbF2 on the spectroscopic, lasing and structural properties of Yb3+-doped fluorophosphate glass

Effect of PbF2 on Yb3+ -doped fluorophosphate glasses is studied. Results indicate that proper amount of PbF2 has absolute advantages in improving the crystallization stability of fluorophosphate glasses. T, value performs a decreasing and increasing tendency with 25 mol% PbF2 as the turning-point. And the spectroscopic properties such as absorption and emission cross section, effective fluorescence linewidth are apparently enhanced with PbF2 over 25 mol%. Lasing parameters beta, I-sat and I-min increase slightly with the addition of PbF2. Raman analysis proves that over 20 mol% PbF2, destroys the phosphate vibration groups greatly. (c) 2005 Elsevier Ltd. All rights reserved.