Atom guiding and cooling in a dark hollow laser beam

We propose and analyze theoretically a scheme for atomic guiding and cooling in a dark hollow laser beam generated from the collimated output beam of a LP01 mode in a micrometer-sized hollow optical fiber. In the scheme, cold atoms from a magneto-optical trap are loaded into the blue-detuned dark hollow beam, move down in the dark hollow beam, and experience transverse Sisyphus cooling induced by the dark hollow beam and a weak repumping beam. In the longitudinal direction, the guided atoms experience heating from the gravity field and cooling from the upward-propagating dark hollow beam and repumping beam. We estimate the transverse two-dimensional equilibrium temperature, the final longitudinal mean velocity, and the total loss of the guided atoms. Our calculations show that a transverse equilibrium temperature of similar to 1.2 mu K, a final longitudinal mean velocity of 0-4.41 mis, and a guiding efficiency of 65-95 % may be obtained.