Science Fiction

I don't think it would be a good idea.

-Lightsabers can reach temperatures ranging from 18,000°C to 25,000°C

-A temperature as low as 300 ºC can lead to dry grass catching on fire

So, pretty good chance of just burning all the grass on your lawn, and your house to. But, lets say you can swing it fast enough so that there isn't enough time for the grass to catch fire, it still cuts the grass by burning it. So at the very least all the blades of grass would have black burned tips on them. I couldn't find any information on how damaging it is to grass health by cutting it with heat however, so I cannot say if doing this regularly would cause your grass to die.

But, I did find this video about a guy who decided to mow his lawn with a laser. You can see how damaging the heat is to the grass.

It would probably be better to have a droid that pushes a reel-type lawn mower around.

Even functional laser cutters things people have done have problems. One is that they leave mulch on top. Another is that they scorch the top of the blades and that’s worse than simple cutting.

A robot that sweeps the clippings up and goes out every couple of days would be the best in that set up. And I already happen to have one.

The technology could maybe have application in welding. Especially if it could deposit filler materials. (Plasma deposition, maybe?)

What's the problem with dropping a lightsaber to the Earth's core? I mean, other than losing it.