Abstract

We present a new mechanism for reaching quantum degeneracy of a 2D bosonic atomic gas. We use the dipole force created by two evanescent waves of different colors to confine ⁸⁷Rb atoms in a quasi 2D geometry. The Morse like resulting potential has a depth on the order of 100 μK. We also present a loading mechanism for this trap, taking advantage of the potential profiles of different Zeeman sublevels. The evanescent waves are produced by two modes of a slab TiO₂ dielectric waveguide : one TM mode is red detuned (δ™ < 0) with respect to the D₂ line of ⁸⁷Rb while the other is a blue detuned (δ^TE > 0) TE mode. The decay length of the TE mode is very small, leading to a short-range repulsive potential, whereas the TM mode creates a long-range attractive potential. Moreover, since the polarization ê of the red-detuned evanescent wave is nearly circular, the attractive potential depends on the magnetic sublevel : it is more pronounced for m_F = −1 and leads to a potential well for this state, whereas the atoms in m_F = +1 see only a repulsive potential. Finally, the expression of the potential for the |F=1,m_F〉 state reads: $\text{U}(\text{z})=\frac{\hslash }{12}\frac{{\Gamma }^2}{{\text{I}}_{\text{sat}}}\left(\frac{{\text{I}}_{\text{o}}^{\text{TE}}}{{\delta }^{\text{TE}}}{\text{e}}^{-2 {\kappa }_{{\text{TE}}^{\text{z}}}}+\frac{{\text{I}}_{\text{o}}^{\text{TM}}}{{\delta }^{\text{TM}}}{\text{e}}^{-2{\kappa }_{{\text{mM}}^{\text{z}}}}\left(1-\frac{{\text{m}}_{\text{F}}}{2}\left|\mathrm{Re}{\widehat{\epsilon }}^{*}\wedge \mathrm{Im}\widehat{\epsilon }\right|\right)\right)$ with Γ the natural linewidth, I_sat the saturation intensity, κ_TE(TM) the evanescent decay length of the TE (TM) mode. The total potential is plotted on the figure for different m_F states.

© 2000 IEEE