By the way, if lasers don't dissipate energy (apparently not at all if we believe you) then why did the SDI lasers they were trying to develop in the 80's require 10 exp 16 watts of power? Granted, they're burning metal, but metal should take NO WHERE NEAR 10 exp 16 watts to burn. Where's the dissipation occuring? This is one reason why SDI was so difficult to achieve, remember?
There is a significant difference between knocking down an ICBM and burning a retina.
And you don't need 10^16 W to knock down a missle.
SDI, was some silly nuclear driven X-ray laser idea.
Modern megawatt class COILs are capable of intercepting missles but the atmospheric abberation correction is tricky.
You are mixing the term "power" with the term "energy". They are not the same thing. If a laser has a very short pulses, it could have very high peak power, and yet not all that much energy or average power transmitted. OTOH, if it's a continuos laser, then the average power is the same as the peak power. Power is in watts, energy in joules (watt seconds) Thus the 50 watt laser, if continuous, delivers 50 joules every second. But if the laser has a microsecond pulse at the rate of one pulse per second, then it would take a 50 Megawatt peak power to deliver the same average power, or energy per second.
Depends on the pulse width and the beam width. If the pulse is a microsecond and the beam disperses enough and if they expect the target to be a polished surface over ceramic then it might require that.