Hi,
This paper shows the setup for generating a light beam with variable OAM, using a variable phase delay box:
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I think the way it works is the two coherent beams are polarized 90 degrees to each other, and then one of them has a phase delay put on it, which creates the non zero OAM resultant combined beam. I am not
100% sure that is how it works, but there is a diagram in the article showing the setup. So it takes phase as well as polarization to make a "vortex beam" so seems like not a good idea for increasing communications bandwidth to me.
cheers, Jamie