How twisted light transmits data faster than ever

Want to know why your cellphone service sucks all the time? Phone companies will tell you: it's bandwidth, man. The wireless spectrum is getting crowded and there's just not enough room. What's needed is a new way to cram more data into the same amount of space, and the solution might be to twist multiple light beams together into a vortex.

Whether we're talking about lasers or radio waves (which includes Wi-Fi), it's all just different wavelengths of light. "Wavelength" is one property that light has, but there are lots of other properties that define a beam of light, including what's called "orbital angular momentum," which specifies how much a beam of light twists as it propagates through space. I know it's weird to think of a beam of light twisting at all, but it helps a little bit to think instead of a single photon rotating around in a circle as it moves forward, creating a spiraling (or helical) path instead of a straight one. Read more about this (with helpful animations) here, but this image should give you a pretty good idea of what the photon/light wave is up to:

oam_spiral.jpg

And here's what some of those different twisted beams of light actually look like:

61079971_spiral_nature_304.jpg

The useful thing about spiraling beams of light is that to some extent, there's an infinite number of different states in which the photon can be made to spiral. It can spiral clockwise, or counterclockwise, in tight spirals or lose ones. Each one of these states can be uniquely identified, but more importantly, you can wrap different spirals up with each other into one single beam. What this means is that it's possible to take two spiraling beams, each containing a unique stream of data, combine them into one beam for transmission, and then unwind them and get both data streams back out again, effectively doubling your bandwidth. Or you can twist four beams together and quadruple your bandwidth. Or how about octoupling it with eight beams? Yeah, that sounds good:

eight_twist.jpg

This image represents eight individual 300-gigabit visible light data streams that researchers from the University of Southern California, NASA's Jet Propulsion Laboratory, and Tel Aviv University twisted together into one single data stream carrying a whopping 320 gigabytes per second. This is a huge amount of data, and the twisted light technique has the potential to make wireless bandwidth a thing of the past. As with all new technologies, consumer hardware and software have a long (long long long) ways to go before something like this will get crammed into your cellphone. We'll be waiting.

Nature, via ExtremeTech

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