Cooling in an optical lattice for a caesium fountain frequency standard

We report progress toward a Cs-fountain frequency standard operating in the nanokelvin temperature range. We have implemented the Raman sideband cooling in a far-off-resonance optical lattice and observed subrecoil temperatures of 200 nK. We have studied the structure of the lattice and optimized the capture of atoms released from the magneto-optical trap into the lattice. In addition, the atoms, accumulated by the cooling scheme in the stretched magnetic state m_F=3, have been transferred to the magnetically insensitive state m_F=0 by using the adiabatic-passage technique.