CILAS SLD400 uses an optical head (diode laser with video or thermal camera) detects sniper's optics. July 1998 (issue 150) of Revue Aerospatiale. French system.
Have no doubt Sandia Labs in Albuquerque and Los Alamos National Labs in Los Alamos are on top of anti-sniper technology.
The airborne laser is being developed as part of the anti-ballistic missile defence here. Some of these people go into bubbles in other parts of the world just to chat.
The phrase, "Go ahead; make my day," takes on even greater irony.
Though, eventually, the technology will end up in the wrong hands. Still, but that time, we ought to have something better.