Boffins shrink light-twister to silicon scale, multiply bandwidth 10x

Vaporware

There are some problems with the "10-fold increased bandwidth". Fortunately, the boffins were not required to transmit 10x more data to publish their paper, but a bit of pixie-dust did the job all-right. Let me explain why this is vaporware (you'll need some patience to go through the following explanation).

Physics tells us that there are three spatial dimensions (for simplicity, let's call them x,y, and z). One dimension will be the propagation direction of the light beam (usually we'd call that the z axis) and we can now freely choose any polarization state and position in the x and y axis.

Any polarization state sounds like a big amount of freedom, doesn't it? Hey let's use it to transfer data! That's the underlying concept of the orbital angular momentum = increased bandwith community. Unfortunately, there are only two spatial dimensions, so the sum of two polarization states (with respective amplitude and phase properties) are sufficient to describe any possible polarization. Commonly, physicists would describe that 'any polarization' state as a sum of x- and y- polarized light, or (perfectly equivalent) as a sum of right-handed and left-handed circularly polarized light. The circularly polarized description is better, it describes the same physics but it allows us to talk about angular momentum and that does sound great! Back to that great freedom of 'any polarization' . The laws of physics boil it down to only two distinct polarization states and that is surely a bit disappointing (where is my factor 10!?).

Now a smart kid might argue that we should relax a little and look beyond x and y: why not use some +-45 (= pi/4) degree angles between x and y as a third and fourth polarization state? Bandwidth, here we come! Unfortunately, those +-45 degree photons have a big propensity to be observed as either 0 degrees (x-axis) polarized photons or 90 degrees (y-axis) polarized photons. So we'll have to collect many photons to tell the difference between our four polarization states and that will slow us down sufficiently to destroy all the extra information we wanted to send along.

How about using the light phase to transmit data? The phase of a photon can take any value between 0 and 360 degrees, so all we have to do is encode information in there. Unfortunately, the phase is only a meaningful concept if we can relate it to a common time frame. If I wait for 1/4 of the period of the light wave (some 3.3 femtoseconds for micrometer wavelength light in your glass fiber), then the phase will be shifted by 90 degrees. We have no detectors that could directly detect such tiny time/phase-shifts of an electromagnetic wave. The only practical way to determine such shifts is to overlap two beams of light and observe their interference (two identical beams will destruct one another if their phase is shifted by 180 degrees). But if we need to send two beams to make use of the phase information, then we might as well use the second beam to transmit data independently. It turns out that the maximum amount of information that can be transferred does not change if we use simple interferometric tricks.

Now you should be ready for the big question. If the simple physics just gives us a factor 2 through polarization and nothing from the phase, how do those boffins magically increase the information bandwidth of light? (They do so on paper at least.) And the answer is simple again: They spatially displace the beam along the x and y axis. Imagine you send beams to different spots -- you could use a separate detector at each target spot and, with 100 detectors, you could increase the information 100-fold! Sounds magical? Not really, it sounds a bit trivial. (Aren't those boring telecoms already using fiber bundles to send multiplexed data?) But that's just because the idea was badly presented.

Let me try again. Imagine we use some interference tricks to control the direction of the light beams. I am sure you have heard about light diffraction, holographic gratings, and other magical tricks. No need to understand them, it's just some interference tool to control the direction of light waves and a few dollars can get you yours! Use this holographic magic to control the x/y spatial direction of the propagating light and you can start aiming at your 100 detectors. Now stop talking about space, that's a bit boring. We use light-waves, and space can be perfectly described as the Fourier domain of an interference mask. Even better, let's describe the interference in terms of circularly polarized states and angular momentum. Remember, I told you the circularly polarized description sounds better! So now we use orbital angular momentum to multiplex the bandwidth of information transmission. That does sound quite nice, doesn't it? Sprinkle some math describing the light interference onto paper and, voila, you get a tenfold increase in bandwidth, together with a science paper and lots of attention.

To be fair, the authors never talk about a tenfold increase in information bandwidth in their paper. So maybe we should assume that the general press (including TheRegister) mis-interpreted the word "potential in the manuscript. Or maybe nobody bothered to read the article, after all there is a press release, which is "able to carry 10 times or more the amount of information than that of conventional l̶a̶s̶e̶r̶s̶ " scientific publications.

It's not the first time I wrote about OAM information transfer magic in the comments. Hello, Richard Chirgwin, are you reading this? It's almost as much fun as the information teleportation magic. But now I ask TheRegister to cease and desist that nonsense for at least 2 weeks, or else I'll spam your comment section with 100 pages from the Messiah. The real Messiah.

Light is the exact same thing as radio waves (just shorter)

Has anyone translated this "new technology" into radio waves and actually demonstrated it?

We live in the age of B.S. hype. I don't know what to believe anymore.