Not a problem. It depends on the kind of lasers. In the "West, land of the free" mostly fiber lasers (based on solid state lasers) are used whereas lower energy fiber lasers are stacked together to get the needed power output. But this has limits, e.g. fiber stacking . Fibers has a limit at their boundary layer where the laser comes out. Also the technique to collect multiple single lasers with a special reflector into "one" laser beam or send multiple single lasers on one point at the target is very difficult and needs high precision. Me self see a limit in power with all these techniques cause of limits of each material what is used for these techniques. Me think that going the way of "laser emitting out of Bose-Einstein-condensate" or "emitting laser out of a magnetic field" are the more powerful versions, enough to shot down missiles hundreds of kilometers away. But long way to go.