B-52s Would be better...

The B-52 has hard points inboard of the 3/4 and 5/6 engine pods that could easily handle a 750Kg, refrigerator-sized, death-dealing, 150Kw LASER. I've heard that it is about 20% efficient, meaning you'd need a 750Kw generator. Now the AF has just ordered a boatload of 800Kw generators, squeeze it down to fit inside a bomb bay, one for each weapon, pipe in JP-5 from the humongous fuel reserves (and It's in-flight refuelable so no worries about running out of gas), and voila! I present you with the LASER-Mega-Fortress. Probably have to re-designate it as the B-52L.

With two lasers on board, the crew would have the ability to tackle multiple targets, or be really nasty and slice/dice together. Put one over an inbound armada and you've got protection from SAMs, enemy aircraft, etc. Put a couple ground-based versions around a military outpost with clear fields of fire and you've got protection from mortars, rockets, cruise missiles, probably even dumb bombs (given enough time to burn through a casing).

Mistake

Just noticed that it's the B-1 bomb bay this thing is being engineered for. This makes more sense than putting it in the B-2 as they are indeed higher value targets.

Yes Shadowdoc, I accept all your points. The only problem at the moment is that there isn't enough internal room on an F-22 or F-35 to fit it inside, hence you would have to carry it on an external pod, ruining the stealth on both of these planes.

Let's put that argument on its head and say the Russians develop such a pod for the Su-35K - or the Europeans fit it to Eurofighter. In an engagement F-22 launches its missiles and becomes visible to radar when the missile bay door opens and IR (PIRATE sensor or whatever) because of the missile plume. Because of advanced fusion of sensors, the non-stealth has a cue for a shot at the F-22 using the laser that has a pretty good chance of hitting, plus the non-stealth missile (AIM-9/120) could easily be shot down by the laser as well.

Btw, these planes still have an IR signature, as well as a small radar one. Missiles can still be used against them, but you have to get a lot closer to make the shot count...

Not necessarily for the B-2

Much better application on the F-22 or F-35, especially for air-to-air engagements replacing the 20mm cannon. Longer range, no need for deflection shooting and firing time for destruction of the target is probably equivalent. If you look at the size of the cannon plus the ammo container, that's probably refrigerator-sized in volume if not shape.

Not only that, but you don't have to worry about housing ammo that can explode on places like an aircraft carrier, and a 150KW laser that fits where an M61 Vulcan fits will also be substitutable for the 20mm cannon on the Phalanx CIWS, with the same advantages -- more range, less to compute. Part of the problem with using the Phalanx as a counter-artillery or counter-mortar platform is that you're throwing a lot more into the air than is coming down, and all of it may be falling on civilian areas. With the L-CIWS, you're not doing anything other than detonating the incoming round, which makes for less of a problem. If this is feasible, I wouldn't be surprised to see the Israelis buy a few for their borders. Launch all the Katyushas you want, as long as they have diesel for their generators or connection to the grid, it's going to be hard to get through.

The anti-laser missiles are going to be rather tough to engineer. Metamaterials aren't necessarily aerodynamic, and every missile that has to carry an ablative coating is that much heavier. You can spin the missile and cause the laser to fire longer to generate enough heat on a given spot to cause structural failure, but that only delays, not defeats the blowtorch that appears on the side of your missile airframe.

If you consider that the F-22 and F-35 are pretty stealthy, shooting missiles at them isn't a real bright idea in the first place.

Air targets are the ideal target because for things to fly they have to be light. Tanks can be as heavy as the ground supporting them will bear, and can have aerosol and ablative countermeasures -- along with their own lasers.