J. Mc Laughlin wrote:
Power is not a linear process. Power involves multiplication.

Nobody has said that power is a linear process.
The equation for adding EM powers has been known
for decades and if it didn't work, it would have
been discarded. As it is, one can find the power
density equation in any appropriate physics textbook.
The method of adding powers associated with two
coherent collinear EM waves is:

Ptotal = P1 + P2 + 2*SQRT(P1*P2)cos(A)

where 'A' is the phase angle between the E-fields
of the two waves.
--
73, Cecil http://www.w5dxp.com