Extended Data Fig. 3: Light shift from the transparency beam.
a, Level scheme showing laser-cooling and transparency transitions. b, Schematic of the potential energy landscape of reservoir and dimple for the 1S0 and 3P1 states. Atoms are rendered insensitive to the laser-cooling light by a single vertical ‘transparency’ laser beam (green arrow) containing two frequency components, one for each circular polarization. c, Transition energies to the three \({m}_{{\rm{J}}}^{{\prime} }=0,\pm 1\) Zeeman sub-levels of the 3P1 manifold, referenced to the transition at zero electric and magnetic field (black dashed line). The energy shifts are shown for a single right-hand circular (RHC) polarization (left) and with the addition of the left-hand circular (LHC) component (right). We show the solutions (solid lines) of the Schrödinger equation for the 3P1 manifold coupled by a light field with single frequency component and RHC polarization. In this case, at high laser intensities, the energy of the state originating from \({m}_{{\rm{J}}}^{{\prime} }=-1\) saturates, corresponding to the presence of a dark state. The vertical purple dashed lines show the operating intensities of the LHC and RHC light fields used in the CW BEC experiment, and the purple diamond is extrapolated from the data. The error bars indicate estimates of the ranges in which the light-shifted spectral lines lie.
