'Twisted light' carries 2.5 terabits of data per second

Researchers have clocked light beams made of "twisted" waves carrying 2.5 terabits of data - the capacity of more than 66 DVDs - per second.
The technique relies on manipulating what is known as the orbital angular momentum of the waves.
Recent work suggests that the trick could vastly boost the data-carrying capacity in wi-fi and optical fibres.
The striking demonstration of the approach, reported in Nature Photonics, is likely to lead to even higher rates.
Angular momentum is a slippery concept when applied to light, but an analogy closer to home is the Earth itself.
Our planet has "spin angular momentum" because it spins on its axis, and "orbital angular momentum" because it is also revolving around the Sun.
Light can have both these types, but the spin version is the far more familiar - as what is commonly called polarisation, or the direction along which light waves wiggle. Polarising sunglasses and many 3D glasses work by passing one polarisation and not another.