100% Invisible IR death ray laser!

I built a massive portable laser with a beam that's completely invisible. What could possibly go wrong?

I've built tons of crazy laser devices over the years but until now I had never built a giant IR laser. I decided my life would be better if I built a massive portable IR death ray and then use it on an IR camera.

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My first attempt at building the laser started by tearing down a green laser pointer from eBay. Inside is an infrared laser diode that's used to pump a crystal of neodymium doped orthovandate which then feeds into a frequency doubling KTP crystal to make green light. This process is not very efficient so a powerful IR laser diode must be used. The final product looks awesome on the IR camera and can definitely burn stuff, but I wanted something much more powerful.

I went on eBay and started shopping for huge fiber coupled IR laser diode arrays. The problem is that most of these for sale used online are actually dead, so it took some careful searching to choose one with a lower chance of being dead. The unit I bought is 25W at 975nm and worked flawlessly.

Coming up with a driver for the thing is not as easy as buying an off the shelf circuit as the laser diode takes a whopping 40A at just 2V. To make matters worse, the driver needs tight regulation and protection from ESD so it doesn't get toasted. Luckily I saw a video by YouTuber Marco Reps of him building the exact driver that I needed! I built a driver based on his schematic (with some minor mods) and it worked flawlessly, so a big thank you to him. Marco Reps channel:    / reppesis  

For the telescope collimator, I used fused silica lenses from Esco Optics. I needed material that would work in the shortwave IR spectrum as well as handle the high power laser light without shattering. These lenses ended up working perfect for what I needed.

The final laser is amazing. The beam looks amazing on the infrared "night vision" camera. I can use it to trigger a giant high voltage spark gap, as well as discharge strontium aluminate glow powder. Plus it is really good at lighting things on fire.

One of the biggest issues is that the laser is completely invisible. This makes it incredibly hard to aim and know where it's pointing. I should make a helmet that feeds the output of an IR camera to a screen in front of my eyes as that would make messing with IR lasers much easier.