Of course, you know more about lasers than I ever will, but a laser with even a few watts of power is powerful enough to cause eye damage.

I went to school with a Captain who started the Air Force laser eye protection project. If memory serves, his name was Mike Cox and he was stationed at Wright-Patterson AFB until 1986. He told me the inspiration for the project came from an incident in the Army. An idiot took a laser target designator and deliberately shined it at people. Several of them experienced temporary eye damage. They conducted a test where they quickly flashed a laser across a test subject's eyes. It took him several minutes before he could focus again. Had he been a fighter pilot on a bombing run or any pilot trying to land, he would've been in big trouble.

Like I said, someone could easily take a small laser and flash it across an approaching airplane's cockpit. If it's a busy airport, they can keep trying until they succeed. It'd be far easier than shooting a duck with a shotgun.