You would need a powerful laser to burn off surface of space junk but that's no problem, we've got cutting laser that have been able to do that for decades. It's the focus that's the issue, poor focus wastes a lot of power so you need more brute force light to compensate.
Once you've got something like that in place though there's no problem. The vapour given off by rapidly heated space junk is just gas, by the time it cools down enough to act like a solid again it's too spread out to crystallise - no threat to anything. The propulsive effect you get isn't great, but not so tiny that it isn't worth doing, particularly for junk in low orbits that only need a tiny nudge to skim atmosphere.