Cecil Moore wrote:

With mutually coherent equal-magnitude sources,
the maximum possible peak intensity is four times
the intensity of a single wave, i.e. there is total
constructive interference. (This can happen
at a Z0-match in an RF transmission line.)

For "largely coherent sources" the peak intensity
would be slightly less than four times.

So according to your theory I can take a 1 watt laser, split the beam
into two coherent beams, recombine the beams in-phase together along
the same path thus creating constructive interference, and obtain 2
watts of laser power. Or would it be 4 watts?

:-)

ac6xg