Thread by @Stefan53202737

Russian soldiers in #Ukraine were spoted using "Laser warning devices" to warn them against illumination from Laser sources (range finders etc) for example from snipers or UAV.
See:
defence-blog.com/russias-unusua…
spartanat.com/2023/01/ukrain…

The device is shown here and very likely uses 2 Photodiodes on top (black circles) to detect the laser light. Note that the picture already tells us that they are only able to detect lasers from front/top of the soldier. The russians are apparently using them helmet mounted.

The used photodiodes are very likely Germanium (Ge) diodes, since their operational wavelength is written as 800-1800nm in the manual (@Spartanat has different values?).
thorlabs.com/newgrouppage9.…

The electronic part of the device probably uses a digital or analogue comparator, which compares the photodiode voltage with a reference voltage. If the photodiode is illuminated with enough power to exceed the reference V, the laser warner will be triggered.

@ButtjerFreimann @grndmstrfesxh @CEinherjer @ChristophHorst3 @KampfmitKette @GMonkey2k3 @Kathokalypse @WAJKoenitz
Can you guys spread the thread?

It’s worth noting that laser range finders usually use either pulsed lasers or amplitude modulated lasers. It is thus very likely that the device is using an inbuilt high pass filter to only see higher frequency “modulated lasers”.

This gives several ways to trick the device:
1.)Use laser wavelength outside of 800-1800nm.
2.)Reduce the laser amplitude modulation frequency or repetition rate, because this will be filtered by the high pass.

3.)Increase the aforementioned, because the photodiode detection speed is limited.
4.)Reduce the laser power to not trigger the warning.
I assume that none of this is feasible without replacing parts of the laser range finder etc.

Especially the last one will require the use of eg squeezed light.
Any questions or clarifications are welcome!

#Miltwitter Maybe you can spread the analysis, so Ukrainians might be able to use some of the info?

@threadreaderapp unroll