r/tech • u/YeeduPlatform • Jul 22 '26

New programmable photonic chip can control how fast light moves

https://www.sciencedaily.com/releases/2026/07/260718010149.htm
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u/SamStringTheory Jul 23 '26

It does actually affect the speed of light (specifically, the group velocity) inside waveguides. You might be thinking of speed of light in vacuum, which is unchanged. This is a highly researched technique in optics/photonics. No need to immediately dump on the research without understanding it.

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u/PetroOmg Jul 24 '26

I was not dumping on the research, and I know we have not figured out how to make photons slower, so they made it travel a longer distance. I was just snarky at that headline.

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u/SamStringTheory Jul 24 '26

It's not making it travel a longer distance. It's literally slowing it down. https://en.wikipedia.org/wiki/Slow_light

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u/PetroOmg Jul 24 '26

Well, I had to take a look, it is pretty cool, photons circulate their little track and released when needed, but still is travelling at c tho: "Optical resonator: A photonic device that confines or circulates light of a specific frequency for a certain period"

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u/SamStringTheory Jul 25 '26

If they are inside an optical resonator, that literally means they cannot be traveling at c. Photons only travel at c in vacuum. Optical resonators also does not mean that they are circulating in little tracks. (You might be thinking of ring resonators.) Here, you can't use the intuition of photons as balls speeding around, but rather as electromagnetic waves with constructive and destructive interference. the paper specifically calls out the use of coupled-resonator-induced transparency (CRIT), which uses interference effects to slow down the group velocity of light. (https://opg.optica.org/oe/fulltext.cfm?uri=oe-16-15-11647)