Two-photon, three-or four-dimensional, color radiation memory

Abstract

Three-, and four-dimensional (“3-D” and “4-D”) volume radiation memories store multiple binary bits of information—typically about five to ten and more typically eight such bits—in the same physical volumes on several different photochromic chemicals co-located in the volume. Each of the multiple photochromic chemicals is individually selectively written with an individually associated pair of radiation beams of an appropriate combined frequency—i.e., a “color”—and energy by a process of two-photon (“2-P”) absorption. All the multiple information bits that are stored within all the photochromic chemicals in each addressable domain are read in common, and induced to simultaneously fluoresce, again by process of 2-P absorption. The fluorescence of each of different photochromic chemical in each addressed domain—which fluorescence is selective in accordance with the written state of each such photochromic chemical—is separated from, and is separately detected from, the fluorescence of all other photochromic chemicals because it is of a unique color, and is spatially steered to an associated detector array, normally a Charge Coupled Device (CCD), by a monochromator, normally a prism. Exemplary fluorescent photochromic chemicals are spirobenzopyran, rhodamine, cumarin and anthracene. Suitable groups of photochromic chemicals are formed from individual photochromic chemicals exhibiting narrow, sharp, separate spectra of absorption and of emission suitably distinct from each other, and where no chemical's fluorescent emission energy overlaps the absorption energies of any other chemicals.