Cooling atoms in far-detuned optical lattices

Summary form only given. Our approach to high lattice occupancy requires a way to cool atoms trapped in a far off-resonance lattice (FORL) and an adiabatic compression sequence to increase the spatial density. For the laser cooling to work, the FORL polarizations must be set so that all magnetic sublevels see the same potential due to the FORL. With this condition satisfied, polarization gradient cooling with independent light works at least as well in the FORL at very high atomic density as it does in free space at low density. The 3D FORL is made from three orthogonal standing waves. After cooling Cs atoms in the 3D FORL, we shut off the horizontal lattice beams adiabatically, so that a 1D FORL trap remains. The atoms are left stacked in pancake-shaped distributions, confined to 50 nm in the vertical direction and 0.4 mm horizontally. The trap depth is 200 /spl mu/K, but the atoms have less than 1 /spl mu/K initial kinetic energy, so they are all near the top of their trajectories in the transverse, Gaussian-shaped potential. The atoms collapse toward the center of the trap. At the moment of peak density we turn the horizontal lattice beams back on adiabatically, trapping 84% of the atoms at lattice sites. We finally laser cool the atoms again in the 3D FORL. The final laser cooling causes collisional loss from lattice sites with more than one atom. Ultimately, 44% of the sites have a single atom cooled to near its vibrational ground state. A theoretical model of site occupation based on Poisson statistics agrees well with our experimental results.