Optical potential for atom guidance in a dark hollow laser beam

We analyze the optical potential for atom guidance in a dark hollow laser beam and compare it with that generated by the evanescent wave in a micrometer-sized hollow optical fiber. We calculate dependence of the optical potential on various parameters: radial position r, laser-atom detuning Delta, beam power P-0, and propagation distance Z. We experimentally generated a dark hollow laser beam from a hollow optical fiber with a 7-mu m hole diameter and obtained a coupling efficiency of similar to 50% for the LP01 mode. Our study shows that a dark hollow laser beam can produce an optical potential deep enough to guide cold atoms from a magneto-optical trap. (C) 1998 Optical Society of America.