The nonlinear standing wave establishes an energy coupling between the two intersecting waves, such that one wave can “pump” or amplify the other. For example if B1 is of higher amplitude than B2, then the interference pattern between B1 and B2 reflects some of the energy of B1 in the direction of B2, as in Figure 2 A, whereas if B2 is of higher amplitude than B1, some of the energy of B2 is reflected in the direction of B1, as in Figure 2 B. In fact, whether the two beams are of equal amplitude or not, some portion of B1 is always lost to B2 through the crystal, while some portion of B2 is lost to B1, as suggested in Figure 2 A, so the net energy transfer always flows from the higher amplitude beam toward the lower. That is, the two waves are intimately coupled through the nonlinear standing wave, energy-wise, and this energy coupling is what allows phase conjugation to produce an amplified reflection.
JL,
You don't cite the quotation above, but it sounds like they are describing a setup with Lasers. Lasers Are a "pumped light source".
http://www.rp-photonics.com/diode_pumped_lasers.htmlThat is why they can be tuned and amplified.
They are a fairly coherent source, therefore can readily be 'coupled' by phase conjugation into a Standing Wave.
The "crystal" they mention is most likely a 'virtual crystal' ; which is actually the created standing wave in some non-linear medium (often they will use some layered material depending on the wave length of the lasers).
This set up, with two, three or four lasers (hence your "4-wave conjugation") will create within the N-L medium, in effect, a diffraction grating, or a mirror.
Then the standard calculations for light diffraction, refraction and reflection will pretty much apply.
You are spot on in your thoughts, imo, concerning possible 'super-normal' effects when the lasers (optical, x-ray, or whatever) are pumped up to extreme powers [and/or, i suspect] extreme frequencies;
then "conjugated" in form or phase and in ~Resonance with particular {platonic ?} 3D geometries.
s