Paper detail

Ultra high densities of cold atoms in a holographically controlled dark SPOT trap

We demonstrate an atom trap geometry for 87Rb which is capable of producing ultra high atom densities. Reradiation forces, which usually limit high densities, can be avoided in dark spontaneous-force optical traps (dark SPOTs) by sheltering atoms from intense trapping light. Here we demonstrate a dynamic implementation of a dark SPOT, resulting in an increase in atom density by almost two orders of magnitude up to 1.3x10^12cm-3. Holographic control of the trapping beams and dynamic switching between MOT and dark SPOT configuration allows us to optimise the trapping geometry. We have identified the ideal size of the dark core to be six times larger than the MOT. Our method also avoids unwanted heating so that we reach a record phase-space density for a MOT.