POLARIZATION-GRADIENT COOLING IN A STRONG DOUGHNUT-MODE DIPOLE POTENTIAL

We present experimental and theoretical studies of polarization-gradie nt cooling of metastable neon atoms confined to the dark center of a T EM01 (doughnut) mode. A slow beam of neon atoms is guided and focused inside a blue-detuned and focused doughnut-mode laser beam to a spot size below 10 mu m. The transverse motion inside this doughnut mode is cooled by means of two-dimensional optical molasses. We observed non- Gaussian two-component velocity distributions of which the cold compon ent has a width of down to three recoil velocities. These results are found to be in qualitative agreement with a quantum Monte Carlo simula tion of cooling in one dimension in the presence of an external light- shift potential. For the simulation we apply the recently developed te chnique of quantum-state diffusion with adaptive noise. [S1050-2947(98 )03710-X].