Dye precursor molecules chemically reactive with the light-altered form of light-sensitive molecules to form stable fluorescent dye, particularly for optical memories including two-photon three-dimensional optical memories

Abstract

Dye precursor molecules—normally rhodamine base—held in a transparent matrix are reactive with acids, bases, ions or radicals—and in the case of rhodamine are reactive with acids—to produce dye molecules—i.e., rhodamine—having markedly different spectroscopic properties. Light-sensitive molecules-normally a compound of ortho-nitro-aldehyde, in particular o-nitro-benzaldehyde or, preferably, 1-nitro-2-naphthaldehyde—in the same matrix undergo photochemical reaction when selectively exposed to light so as to form at least one of the acids, bases, ions or radicals with which the dye precursor molecules are reactive—preferably nitroso acid. Chemical reaction of rhodamine base dye precursor molecules with photochemically produced nitroso acid within domains that are radiatively-selected two-dimensionally or within voxels that are radiatively-selected three-dimensionally, by first-frequency “write” radiation—including as may be realized by two-photon absorption—produces stable rhodamine dye in the radiatively-selected domains/voxels. Subsequent illumination with a single, second-frequency “read” radiation induces strong fluorescence in the dye of the written domains/voxels while leaving all chemicals/photochemicals unchanged. The induced fluorescence may be imaged to a detector, such as a charge coupled device (CCD), to reliably realize a high signal-to-noise, non-degrading, optical memory of the write once, read many (WORM) type.