Twisted laser vortex breakthrough: near-infinite bandwidth

[rhoenix]

Scientists at the Stanford Linear Accelerator Center (SLAC) have devised a new way of creating twisted laser beams — optical vortexes — for carrying vast, near-infinite amounts of data down optical fiber, discovering exoplanets, and more. SLAC’s optical vortex technology is much more advanced than previous attempts at creating and transmitting twisted light, allowing for shorter pulses, higher intensities, and much wider wavelengths — including X-rays. These twisted laser beams are so high-fidelity that they actually open up new, unknown areas of science; the tech is so far ahead of demand that scientists aren’t actually sure what they can use it for.

Twisted light — and twisted radio waves, which are the same thing but at a lower frequency — as we’ve covered before, are incredibly exciting because they travel in three dimensions rather than two. Currently, when light travels down a fiber-optic cable between data centers, or a WiFi or cellular radio signal hits your smartphone, it’s traveling in just two dimensions: The signal is, in essence, flat. So far, this method has provided enough bandwidth for our needs — but as our thirst for data increases, and the electromagnetic spectrum becomes ever more congested, research into three-dimensional radio and laser transmission has kicked into overdrive.

In technical terms, electromagnetic radiation — radio, microwaves, visible light, X-rays — can have two kinds of spin: Spin angular momentum (SAM) and orbital angular momentum (OAM). If you imagine the Earth spinning on its axis, that’s SAM; if you picture how the Earth rotates around the Sun, that’s OAM. Currently, we only modify SAM — but by using various methods, we can induce OAM, too. Without turning this into some kind of visuospatial IQ test, trust me when I say that applying both SAM and OAM makes radiation fly through the air in the shape of a corkscrew.

The advantage of using three dimensions is that you can essentially transmit an unlimited number of signals through a given amount of space. Imagine one corkscrew signal, and then another one behind it, offset by just a fraction of a millimeter — and then an almost-infinite stream of further signals after that. You can only squeeze a small number of two-dimensional signals into the same plane, using a variety of modulation techniques, before collisions occur.

Previously we have written about very rudimentary ways of inducing OAM, such as gratings, or physically twisting the antenna (pictured right). The SLAC, however, have used an incredibly advanced method that lends itself towards very precise, high-performance, high-accuracy applications. If you can watch the video embedded above, now would be the time, as it fairly succinctly explains SLAC’s method. Basically, using the Next Linear Collider Test Accelerator (NLCTA), beams of high-power electrons are forced to through an undulator — a chicane of magnets that causes the electrons to form into a helical spiral. They then hit a second undulator, causing them to wiggle and emit light.

The end result is small bunches of electrons that emit twisted laser light (pictured top). According to the researchers, this method can be used to produce transmissions in the hard X-ray range — extremely high-power (100 keV), incredibly dense (100-picometer) waves. The same method could easily be used to produce twisted infrared signals for ultra-high-bandwidth fiber-optic transmission, or for free-space twisted laser light links. The SLAC researchers will now focus on twisting different types of light and electromagnetic radiation — and, curiously enough, actually trying to discover what they can actually do with these new twisted beams. The obvious application is the creation of commercial OAM-based protocols, but the researchers seem confident that their tech is so advanced that it can open up entirely new areas of science and research.

So not only much more information can be compressed into the same space, it's also offering up a new branch of science.