Optical pumping of orbital angular momentum of light in cold cesium atoms

We present experimental results on the transfer of the orbital angular mome ntum of light to a system of cold cesium atoms; A nondegenerate four-wave m ixing process was used as an indirect tool to observe this transfer. Our ex periments show, in particular, that the orbital angular momentum of light c an be transferred, via optical pumping in the cold atomic sample, from one beam to another oscillating at a different frequency.