I remember reading about photonic holographic memory over a decade ago in New Scientist. Someone had built / was building / was thinking of building a cube where you'd have two lasers able to target in x,y and z dimensions of it and where the lasers intersected, it would flip the state of the atom / molecule. Thus you had writable memory that wasn't a thin wafer, but a three dimensional block. Enormous data density was supposed to be possible along with staggering access times. They had some clever way of reading that state back by using one laser, or a lower-energy laser, I forget.
At the time, it sounded fantastic. Anyone know whatever happened to that?