That's not actually a very big concern. Communications satellites are placed in geostationary orbit, which has two important constraints. First, they have an altitude of about 22,236 miles. Second, they can only be placed in the Earth's plane of rotation (which means that they have to be directly above the Equator). The Earth's atmosphere goes about 62 miles straight up, at which point you are considered to be in space (although the atmosphere really continues past that limit, but in a much thinner form). That means that a laser fired would have to travel at least 62 miles through the atmosphere, and likely much more (depending on the angle it's fired at). As it moves through the atmosphere, it will lose significant amounts of energy. Additionally, because lasers aren't perfectly straight (they actually spread out at an angle, or diffuse), the width of the beam would continue to expand over the distance to reach a communications satellite. A 1 degree diffusion straight up would cause the beam to be 388 miles wide by the time it reached geosynchronous orbit. That means that the remaining energy would be spread out over an area of over 118000 square miles. Such a short pulse wouldn't do much of anything to a satellite at that range.