Dark-spot magneto-optical trap of cesium atoms

We constructed a dark-spot magneto-optical trap (MOT) of cesium atoms in a vapor cell. In addition to an opaque dot in the path of the repumping laser beam, we used an independent laser to optically pump the atoms into the dark hyperfine ground state. Fractional population of atoms in the bright hyperfine ground state was as low as 0.056. While the loading rate of a dark-spot MOT was only one third smaller than that of a normal MOT, its loss rate was reduced by a factor of 5, and three times more atoms were present in the dark-spot MOT. Due to the high vapor pressure in our cell, we could not observe any reduction in the density-dependent loss effect in a dark-spot MOT.