Mike Monett wrote:
Since photons do not
interact, EM waves also do not interact with each other.

The following quote sounds like an interaction of photons to me.

http://micro.magnet.fsu.edu/primer/j...ons/index.html

"... when two waves of equal amplitude and wavelength that are
180-degrees ... out of phase with each other meet, they are not
actually annihilated, ... All of the photon energy present in
these waves must somehow be recovered or redistributed in a new
direction, according to the law of energy conservation ... Instead,
upon meeting, the photons are redistributed to regions that permit
constructive interference, so the effect should be considered as
a redistribution of light waves and photon energy rather than
the spontaneous construction or destruction of light."

I suspect that coherent photons can interact at an impedance
discontinuity which causes reflections.
--
73, Cecil http://www.w5dxp.com