Well... supposing anti-photons were to exist, I don't know they would even cause an explosion. I always thought anti-particles and particles ahnihlated eachother releasing photons and energy. a photon and an anti-photon would more than likely follow the same pattern of ahnihlation, releasing particles we can't measure yet, and don't really know about, and again more energy. The question is when positrons jump energy levels, and release energy just the same way eectrons to. If that positron were to release an energy in the form of visible light would it be an anti-photon? Also, there are electromagnetic waves and forces like gravity that can attract light, so one would think there is a similar way to repel light, if you could focus that wave into a beam there should be a cylindar of what would appear to be heightened brightness along the beam, however the center of the beam would certainly appear black, as should a black dot appear on whatever object the beam is pointing at.