  This paper describes an integer multiplier for the orbital angular momentum
(OAM) of light through the parallel implementation of multiple circular-sector
transformations, whereby the cross-sectional circular shape of the OAM mode is
geometrically transformed to the circular-sector shape. Experiments show that
the conversion accuracy of both OAM doubler and tripler formulations is
significantly better than that of the previous method. This is because the
proposed method uses a simple implementation with a single spatial light
modulator. The proposed method has strong potential for the spatial mode
manipulation of OAM and other useful spatial modes.
