Trope-a-Day: Laser Blade

Laser Blade: Dear gods, no.

Firstly and perhaps most importantly, light does not work that way. Most specifically, it does not stop.

Apart from that, you could try and fake it with a hot plasma bottle – if you want a melee weapon that sets everything around it, including you, on fire. And requires a ridiculous amount of power even by the standards of people who pack uranium-fluorine molten-salt reactors into power armor. And takes time to cut and so can’t be conveniently waved through solid objects. And has a hilarious vulnerability to magnets.

…and still doesn’t behave like a magical laser blade.

(There are both laser torches and plasma torches. They’re short-ranged industrial cutting tools, and mostly unsuitable for use as even improvised weapons unless you’re going all No Mister Bond I Expect You To Die cackle-cackle elaborate deathtrap for some reason.)