Help with Raving Neighbour

In answer to the root of your question, yes that is technically possible but no it's not practical.

Also, it depends where in the world you live, but the legality of what you're proposing is questionable at best.

IR is as you know, line of sight (although it does reflect like all light does). And it reflects rather well off window glass, especially if it's dirty, double-glazed etc.

But with sufficient power you can overcome this.

And then the next issue arrives - a Class III, 5 mW laser pointer, is considered safe but it can still damage eyesight if abused (our aversion response usually stops this happening as it's like staring into a sun). 

But infra-red laser diodes, the type that operate in remote controls, those are a different animal and have the potential to cause irreversible partial blindness (through damage to the retina) to total blindness if the beam hits the optic nerve.

I'm open to thoughts from my fellow community members but his gear might not even be IR remote controlled. I'm seeing a lot more Bluetooth units of late, although audio gear is probably IR though.

Law isn't my area of expertise, but used in this way the laser would be classed as an offensive weapon and it's highly likely you would be in very serious trouble if discovered.

Surely there are other ways to get the message across? How old is this chap (approximately)? VHF audio (18-20KHz) can be very unpleasant for young people but we can't hear it over about our mid 20s. That said the idiot is probably already going deaf from what he's subjecting you too.

Which country do you live in? Someone might have a better idea of your local laws then.