That was only one of the SDI investigations. (IIRC, that worked).
The Air Force Airborne Laser uses a Chemical Oxygen Iodine Laser
Specs on the system:
Type : 6 COIL (Chemical Oxygen Iodine Laser) modules in series world's shortest wavelength, high-power chemical laser
Wavelength : 1.315 mm
Weight : 1.5 tons per module (6 modules on ABL)
Power : Megawatt class.
Range : several hundred km (when missiles emerge from above the clouds)
Aircraft : 747-400 commercial freighter
Altitude : 12,000 meters
Notice "Mega-Watt class" not 10^16 watts, only 10^6 Watts.
Yes, this is considerably weaker. One of the SDI proposals was to fire lasers from the ground and up to a mirror. That created two paths for attenuation. Some here are saying that energy attenuation is not that big of a deal (the width of the beam was the big consumer for SDI) but I'm not so sure. Do you know the width/radius of the beam used on the aircraft?