It's well understood that photons carry both energy and linear momentum. It's less widely understood but known for over 100 years that photons can also carry angular momentum. But it's only in the past 20 years that light orbital angular momentum has been studied, and only in the past year or so that serious work has been done with radio frequency photons. Recently I posted the URL of a Discover magazine article, Twisting Radio Waves Could Give Us 100x More Wireless Bandwidth in my Google+ stream (with copies to my Twitter and Facebook streams).
That post prompted one public comment and several off-line email discussions, so let me elaborate. While I don't expect 100x wireless capacity any time soon, this is a real effect that might be used for 2x, 4x or 8x gains within the next decade. Wikipedia has the best visualization:
Thidé et al formed their twisted radio waves by reflecting an RF source off an approximately spiral-formed reﬂector. This is a cool experiment but you'd need a set of reflectors, one per channel, each with slightly different depths of their spirals to begin making wireless capacity gains. To make this commercially viable, we need an antenna that can create several different orders of vortex in the same physical space.
If someone figures this out, then the resulting separate channels could be used directly with MIMO electronics and an antenna that fits in limited space, much as 2x2 MIMO systems use horizontally and vertically polarized antennas that fit in the same physical space.
It will be very interesting to see if someone can come up with an antenna structure that can produce different order spiral vorteces in the same space. In any event, this is an area to watch.