How would I go about Making a Blue, 5mW Laser Pen?

[ClassyLich]

It's been many years since I've done anything with lasers, and I've always wanted a blue laser pen that wouldn't fry anyone's eyeballs; a laser with a power <=5mW. I'm not sure where or how to begin. Are there even any diodes that would work for this?

 

[Thorsteenster]

If you're looking for around 5mw, your best bet maybe just buying a prebuilt on Ebay or the like.
I just purchased a couple diodes recently and had been looking around quite a bit prior to purchase.
The lowest I'd seen was a 50w 520nm, 80w 450nm, and a 50w 488nm.
Maybe one of those could be underpowered to get your desired output, but it'd be some pretty low input and not sure if that's recommended or not as you may not get that much visual of the beam.

On the other hand, with proper safety practices you'll be fine with an eye frying laser. As long as that's not what you're using it for lol

 

[Encap]

Probably cheaper than attempting to make one, ZBolt sells 5mW laser pens, see: https://www.z-bolt.com/guides/