To me at least, beam-powered propulsion seems like a great idea. High specific impulse, non-negligible thrust, and no heavy nuclear reactors on board. It's even been successfully tested by Escape Dynamics and Freeman Dyson is a proponent. Why has no launch vehicle used this technology? Why does there seem to be not much research or development in this area? What are its limitations?
From the Wikipedia article:
The rule of thumb that is usually quoted is that it takes a megawatt of power beamed to a vehicle per kg of payload while it is being accelerated to permit it to reach low earth orbit
Laser efficiency is on the order of 25%. Then there are atmospheric losses, at low altitudes this can be as much as 30% to an altitude of 6 km and distance of 40 km. The most powerful continuous laser available has an output on the order of 1 MW.
So you'd need ~10,000 of the world's most powerful lasers to launch a 1-ton payload into orbit.
At low altitudes, you can use the lasers to heat the atmosphere, but above ~30 km, you need to start supplying propellant, which reduces your payload.
While this idea has some potential, the initial investment is massive. I think that's why beamed propulsion is not used yet.