  Full, three dimensional, time-dependent simulations are presented
demonstrating the quantized transfer of angular momentum to a Bose-Einstein
condensate from a laser carrying orbital angular momentum in a
Laguerre-Gaussian mode. The process is described in terms of coherent Bragg
scattering of atoms from a chiral optical lattice. The transfer efficiency and
the angular momentum content of the output coupled vortex state are analyzed
and compared with a recent experiment.
