I wanted a sprinkler system with lasers instead of water. Pop up, laser the grass in all directions, pop down. Just make sure nobody's in the yard, first. :)
In practice this is probably a terrible idea - your beautiful green grass is constantly being burned on top.
Which is worse, cauterization or hacking with a mower blade?
I'd say cauterization. Wouldn't it prevent the grass from growing anymore, as well as looking terrible (burnt on top)?
Grass grows from the root up, i.e. it's not like a tree. Whether you chop it off with a laser or with high-speed steel, it's going to keep growing from the root; it's evolved to grow after being chopped off by sheep's teeth, after all.