Jim Kelley wrote:
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?

If it were total constructive interference, two 1/2W
beams would yield an intensity of 2 watts. Of course,
at another location, total destructive interference
would have to occur where the intensity was zero.

Put another way, the bright interference rings would
contain two watts per unit area while the flat black
rings would contain zero watts per unit area thus
averaging out to the original total of one watt.

As I said before, this ain't rocket science.
--
73, Cecil http://www.w5dxp.com