LAWS is a relatively low power (kW) system and works by simply heating the target until it melts or burns, this is different to the stars-wars and aircraft mounted lasers that use MW and very high pulse energy to vapourise the target with a single shot.
This kind of weapon has a few problems:
You need to hold the beam on the target for several seconds. But there is enough absorption in the air to heat the air and change the optical properties, so the beam tends to move off target. In the tests the target was cooperatively flying across the view - allowing the beam to move into clean air.
You can lower the energy absorbed by coating the target in shiny aluminium, even exposed to air the reflectivity of Al is >85% at these bands, so only 1/6 of the energy arriving at the target will be absorbed. You can also arrange for the target to have a low angle of incidence surfaces facing the ship.
I suspect it is going to be a lot more effective against slow flying dark painted drones than a supersonic anti-ship missile with a reflective pointed nose cone, coming straight at you for 10seconds.