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Comment by cycomanic | Hacker News Reader

While the experiment is certainly cool, it should be pointed out that this is not a passive process and the demonstration needed a femtosecond laser operating at 830nm with an average power of 10mW. While it might be possible to make integrated lasers with those properties in the future currently they use a Ti:Saphire laser which occupies a space of about 1.5m x 30cm x 30 cm. So clearly not portable.

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That would fit and work on vehicles though, which would let them drive at night without visible lights. So still some good military applications, which means it'll probably still get a lot of funding and someone will probably manage to shrink the laser down quite a bit more. At least with a backpack-able version anyway.

Military vehicles can already drive at night without visible light. Except in the most extreme case (new moon and heavy cloud cover) - and then they can illuminate using infrared. Such a device costs <2,000 USD and is already wearable. More expensive and/or vehicle-mounted systems increase that capability to the point where you basically never even need the IR illumination, unless the vehicle is fighting inside a building (rare).

The technology in the article, aside from being heavily editorialized, will remain inferior to that for a long time. However, one possible application would be the use of higher-wavelength infrared for the active illumination, so that other militaries with night vision are unable to see your infrared headlights and then blow you up.

IR illumination (no matter the wavelength), or this laser-based night vision, would light up a military vehicle like a big bright target. For night vision to be viable in a military setting, it needs to be passive.

Is it possible to design ultra wide spread spectrum light pulses that are below the signal to noise ratio if you don't know the code? At least some RF signal sources are at least difficult to detect I guess.

The problem with illumination is that it’s easy to pick up stray rays from the light source. Hence why infrared is preferred.

Not too long ago, some luxury cars had an optional built-in night vision display, but as far as I know, they've stopped offering that feature, not sure if it was just ineffective or too inexpensive. As I age and my night vision degrades, I'd be really happy for a car with night-vision built-in, even if it meant wearing a headset or goggles.

https://www.autobytel.com/10-vehicles-with-night-vision

I'm curious as to the potential harm concentrations of light can be, even if outside the human visible spectrum. Not just to people, but wildlife and plantlife.

True currently, but laser form factors are shrinking quickly. Reminds me of this article from a couple months ago where a team built (among a host of other sizes/use cases) a 20W(!) laser using a 500um PCSEL which they describe, mounted, as "roughly the size of a webcam". Their lasers are also at comparable wavelengths

https://spectrum.ieee.org/pcsel

The laser doesn't seem to be a core requirement of the system, it's mainly used as a very short bright illumination source and isn't part of the up conversion system.

The full experimental setups are available in the supplemental materials: https://onlinelibrary.wiley.com/action/downloadSupplement?do...

Full paper: https://onlinelibrary.wiley.com/doi/10.1002/adma.202402777

Seems like it could be done with mode-locked fiber. It’s just easier to get high-Q with a tabletop setup. I’m bullish on hollow core to solve that too.

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