Optical Molasses and the Orbital Angular Momentum of Light

Zhengling Wang, Jianping Yin

Christoph Gerz, Theodore Hodapp, Poul Jessen +2 more

Xizheng Ke, Hong Lv, Jingzhi Wu +1 more

The beam with orbital angular momentum is a present domestic and foreign research key direction. Its application and development will bring the profound influence in the optical communications field. At the same time, light's orbital angular momentum promises potential applications in both classical and quantum optical communication. The research progress of the beam with orbital angular momentum and encoding information as light's OAM for free-space optical communication were reviewed in this article, the existing design method, mechanism and description methods of encoding information as light's OAM were discussed. In quantum communication, qudits can be encoded in photons using their OAM for creating high-dimensional entanglement based on entangled photon pairs from SPDC. In this paper, light's OAM is used as information carrier for classical and quantum communication, which is promising to ensures the security of atmospheric laser communication, improves the density and precision of information transmission. It is apparent that an efficient way to measure the orbital angular momentum of individual photons and light beams with good efficiency would be of potentially great importance for optical communications and quantum information. In view of the above, the measurements of orbital angular momentum of individual photons and light beams are analyzed and discussed in detail.

P. L. Gould, Paul D. Lett, William D. Phillips

A. R. Carter, M. Babiker

We explain how a proper specification of the spatial field distribution and angular momentum content of a twisted light beam propagating in an arbitrary direction can be made using appropriate transformations. Such transformations are needed whenever a light beam is to be combined with other similar beams propagating in specified directions. The transformation procedure greatly facilitates the evaluations of the radiation forces acting on atoms subject to an arbitrary set of twisted light beams. It allows atomic trajectories in one-, two-, and three-dimensional optical molasses configurations to be correctly evaluated. We find that multiple twisted beams offer a flexible means of controlling the motion of atoms, but there are notable features attributable only to the orbital optical angular momentum property of the twisted light. Under suitable conditions, atoms can be decelerated and ultimately made to congregate in specific regions of space. The implications of this for all-optical atomic cooling and trapping using twisted light are pointed out and discussed.

P. L. Gould, Paul D. Lett, William D. Phillips