Selected domains, normally 2x103x2x103 such domains arrayed in a plane, within a three-dimensional (3-D) volume of
radiation-sensitive medium, typically 1 cm3 of spirobenzopyran containing 2x103 such planes, are temporally and spatially simultaneously illuminated by two
radiation pulses, normally
laser light pulses in various combinations of wavelengths 532 nm and 1024 nm, in order, dependent upon the particular combination of illuminating light, to either write binary data to, or read binary data from, the selected domains by process of two-
photon (2-P) interaction / absorption. One
laser light pulse is preferably directed to illuminate all domains during its propagation along one directional axis of the volume. The other
laser light pulse is first spatially encoded with
binary information by 2-D
spatial light modulator, and is then (i) directed and (ii) time sequenced to intersection with the other light pulse in a locus of intersection domains. During writing the selected, simultaneously illuminated, intersection domains change their index of
refraction, attendant upon a change in isomeric molecular form, by process of 2-P absorption. During reading selected intersection domains selectively refract each of two read light pulses identically-as well as fluoresce-dependent upon their individually pre-established, written, states. The selective
refraction of each read pulse in its passage straight through the volume is sensed in a
detector array. I / O bandwidth to each cm3 of
radiation-sensitive medium is on the order of 1 Gbit / sec to 1 Tbit / sec.