The vacuum being optically linear medium, there is NO interaction between photons and/or optical waves, however you look at this. (there is some theoretical work about possible interactions between very high energy photons and radio-waves (when I dig the paper out, I will post it here..
http://en.wikipedia.org/wiki/Two-photon_physics) , but I am not sure if this was ever confirmed by experiment or observation).
However, photon-photon interactions will occur only in optically non-linear media, like some crystals, and this effect is used in lasers, optical (EDFA) amplifiers, optical frequency doublers and so on. Of course, in such environments the atoms in crystal lattice play the important role in those interactions.