YouTuber Styropyro came up with about as close as you can get to an actual working DIY lightsaber by crafting a portable 7W blue laser then proceeded to see just what he could do with it.
As he notes, an actual Jedi-style lightsaber faces a number of tech issues such as being able to carry enough juice to be worthwile, and, of course, producing a directed light that is confined to saber-length.
Noted for his past efforts at making a 40W laser shotgun, Styropyro was able to kinda pull off the first one and had no hope of the second one
“My device uses a Nichia GaN laser diode, which was overdriven to 7W of output by running it at 4.6A with a couple high efficiency buck drivers in parallel. An anti-reflective coated glass lens focuses the beam, and the whole device is powered by two unprotected 18650 batteries in series,” he says.
The underwhelming results include the ability to cut soldering iron, engrave on wood, spark plasma and blind you “instantly and forever.”