Enhancement of Sisyphus cooling using a bichromatic standing wave

We show that Sisyphus cooling in a one-dimensional gray optical lattice can be improved by using a bichromatic standing wave that increases the efficiency of cooling as compared to typical lattices. Using the time of flight technique to determine the velocity distribution of all the atoms, we calculate the efficiency by measuring the fraction of all atoms that are cooled by the lattice. We show that the efficiency depends on the relative displacement between the two standing waves formed by the two colors. The optimal configuration of the bichromatic light field yields a 40% improvement in efficiency compared to typical optical lattices, while maintaining the same atomic temperature.