Corkscrewing Lasers Could Be the Key to Unlimited Bandwidth

By Andrew Tarantola on at

Conventional data transmission techniques rely on two-dimensional signals to carry the information down a pipeline, but there's only so much potential bandwidth to go around. There are only so many signals you can pack into a given plane before they begin to overlap and interfere with another. But if we were to add an additional third plane, science could conveniently sidestep that technological roadblock. And that's exactly what a team at the Stanford Linear Accelerator Centre (SLAC) has done.

We've known about optical vortexes—wherein light rotates around the axis of its travel in a a corkscrew pattern—since a pair of Princeton researchers first identified the effect in the mid-1970s. Electromagnetic radiation—whether it's visible light or microwave beams—exhibits two types of spin: Spin Angular Momentum and Orbital Angular Momentum. The difference can be visualised as the Earth turning on its axis (SAM) versus the Earth revolving around the Sun (OAM). Conventional 2D modulation only affects the signal's SAM, moving the wave up and down. But, by manipulating a signals OAM in a 3D plane, we could theoretically at least, generate a near-infinite number of offset corkscrew-shaped signals within any given transmission space.

Earlier this year, a Boston University team tinkered with OAM modulation and was able to eclipse 1.6 TB/sec transmission speeds. As the lead investigator explained:

A typical cable Internet connection to a home delivers 1-10 megabits per second of data, which means that the transmission capacity we demonstrated with OAM modes in our fibre represents a capacity equivalent to one million simultaneous cable-internet connections today.

Unfortunately, OAM modulation techniques are still in early development and are rather imprecise. However, SLAC researchers have now taken the BU concept and run with it. The SLAC researchers fire a powerful electron beam from the Next Linear Collider Test Accelerator (NLCTA) through a pair of undulator systems that first cajole the negative stream of particles into a corkscrew shape and then enticed to emit light by means powerful electromagnets set up in series.

The resulting emission is a stable twisting pattern that can accommodate massive energy levels without braking down. We're talking hard X-rays in the 100 keV range with unprecedented 100-picometer wave densities. This is great news since it means that with a bit of fiddling, researchers shouldn't have much trouble adapting the system to modulate and transmit weaker forms of EM radiation including microwave, infrared, or optical light.

While this discovery could eventually lead to fibre-optic transmission speeds multiple magnitudes faster than they are today, the technology is so new that researchers still haven't quite figured out what it would best be suited for. And you thought Google Fibre was fast. [Nature via Extreme Tech]