Generation of a dark hollow beam by a four-step phase plate and its application for manipulating cold atoms

In this paper, we propose a new scheme to generate a dark hollow-beam, which includes dark hollow-beam optical pipe and hollow-beam optical dipole trap, through using a system composed of a four steps phase plate and a spherical lens. This kind of light beam can be used to focus, guide and trap the cold atom. We also calculate the intensity distributing and characteristic parameters of a dark hollow-beam and the optical dipole potential which manipulate the cold atoms of 85Rb. At last, we analyze and demonstrate the experimental feasibility of the scheme.