  The microwave-induced orbital angular momentum (OAM) transfer from a
Laguerre-Gaussian (LG) beam to a weak plane-wave is studied in a closed-loop
four-level ladder-type atomic system. The analytical investigation shows that
the generated fourth field is a LG beam with the same OAM of the applied LG
field. Moreover, the microwave-induced subluminal generated pulse can be
switched to the superluminal one only by changing the relative phase of applied
fields. It is shown that the OAM transfer in subluminal regime is accompanied
by a slightly absorption, however, it switches to the slightly gain in
superluminal regime. The transfer of light's OAM and control of the group
velocity of generated pulse can prepare a high-dimensional Hilbert space which
has a major role in quantum communication and information processing.
