We present experimental and numerical studies of the atomic motion in an optical lattice displaying a fivefold rotational symmetry. The atomic transport has been investigated by measuring the time evolution of the size of the atomic cloud. The experimental results are compared to those of a semiclassical Monte Carlo simulation of the atomic motion in a three-dimensional optical quasicrystal. A good agreement has been obtained on the anisotropy of the diffusive expansion of the cloud. ͓S1050-2947͑99͒50312-0͔PACS number͑s͒: 32.80.Pj, 61.44.Br RAPID COMMUNICATIONS R4234PRA 60 GUIDONI, DÉ PRET, DI STEFANO, AND VERKERK RAPID COMMUNICATIONS R4236PRA 60 GUIDONI, DÉ PRET, DI STEFANO, AND VERKERK

The properties of the hollow beam produced by a conical lens are studied in detail. In particular, the impact of a rounded vertex is examined. It is shown that it could lead to drastic changes in the transverse distribution of the hollow beam, determined by the ratio between the transverse size of the incident beam and the size of the blunt area. An adequate choice for this ratio allows us to either minimize the losses or optimize the distribution symmetry.

No abstract