Orbital Angular Momentum of Light | Hacker News Reader

Orbital Angular Momentum of Light

en.wikipedia.org

I swear these random Wikipedia articles posted on HN now and then is like aliens/time travelers nudging us towards higher technology :)

I have never been able to understand light and I probably never will. Electromagnetism in general. Like actually wrap by head around and grok it intuitively

I suspect that feeling you have is because collectively we don't yet fully understand what light is. That's why theories about it are still not as elegant and simple as the material phenomenon is in its esssence.

About visitors from the future or an extraterrestrial civilization dropping subtle hints in our field of consciousness to nudge us all toward higher technology - there's an immense space of unimaginable possibility that we probably wouldn't even notice what happened until we reach the next level of that transformation and evolution, and reflect on how we got there.

> reflect on how we got there.

I'd say the breakneck speed of progress in the last 100 years.. in just like a 0.0001% of humanity's total history.. is pretty sus tbh :)

From the first barely flying airplane to rockets and satellites, from formalizing mathematical logic and figuring out basic physics to harnessing nuclear energy, building a world full of computers, robots and artificial intelligence. That leap is a blink of an eye in the scale of time, like snapping your fingers and shazam! The planet awakens.

Check out some of the plots here https://en.wikipedia.org/wiki/Technological_singularity

Though many events are cherry picked, the trend is still quite a nice fit it seems. I would say exponential growth is rather plausible.

In fact it doesn't even need to take aliens to change our timeline. In Cosmos by Carl Sagan he often talks about so and so Greek guy that was basically correct but dismissed. They had some inkling of the experimental method but didn't pursue it. They knew about the motive powers of steam. They just didn't think much more of it I guess.

Why Ancient Rome, Greece, or even the Ancient Egyptians 5000 years ago didn't start an industrial revolution even though they had the manpower and maths to build the Pyramids, is always a fun "what if" alternative history to think about.

> Research into OAM has suggested that light waves could carry hitherto unprecedented quantities of data through optical fibres. According to preliminary tests, data streams travelling along a beam of light split into 8 different circular polarities have demonstrated the capacity to transfer up to 2.5 terabits of data (equivalent to 66 DVDs or 320 gigabytes) per second.[40]

> [40] https://www.bbc.co.uk/news/science-environment-18551284

Fun!

Note that we could already theoretically pack data into separate spatial modes (c.f. [0]), but the problem is in a real fiber, energy will leak from one mode into another, limiting useful signal. Compounding this is that different modes can propagate at different velocities, so you can e.g. have energy leak from mode A to B, travel more slowly for a moment, then back from B to A, which effectively smears your A signal even if you filter on the ends. This is why single mode fiber (i.e. fiber thin enough that only the single 00 mode fits) is used for high data rates/long distances. The same thing can happen with polarization modes, which you can't eliminate by just making your fiber smaller, so IIRC they are actually the enemy. So there are real engineering challenges to actually make extra channels be useful rather than harmful (this is all recollection of uni courses 15 years ago, but it seems single mode fiber has only become more popular, so I suppose it's still an issue).

[0] https://en.wikipedia.org/wiki/File:Intensity_profiles_of_Lag...

What about for laser connections like with Starlink?

I would imagine lasers are different because they're a coherent beam.

I OAM is used, it means switching to ring-core fibers.

Man, we've come a long way since "An Evolved Circuit, Intrinsic in Silicon, Entwined with Physics" (1997)

https://gwern.net/doc/ai/1997-thompson.pdf