Ultra-high Density Optical Memory Media

Future Command, Control, Communications, and Intelligence (C3I) will be extremely high density and more compact memory media not presently available. Rewritable multi-layered optical storage media promise to increase removable disk computer peripheral storage capacity by two orders of magnitude. Two-photon excitation of photosensitive molecules at the focus of a high numerical aperture laser beam provides unparalleled optical sectioning (axial resolution), allowing stacking of up to 100 data layers within a single unified composite disk. Several background suppresion methods may be used for reading: either confocal detection of two-photon fluorescence excitation for fluorescent photochromic media; differential interference contrast detection (DIC) for phase recorded media. We have already achieved "write-once, read-many" (WORM) media at densities of > 10 12power bits/cm3 in 30-layer photopolymer phase recorded structures. Here we propose to extend this work with the development of erasable or "rewritable" media. During Phase I, several proposed photochemistries including: bacteriorhodopsin, polyester with azo-dye side groups, and fluorescent photochromic media will be evaluated in terms of relative stability, cyclicity, toxicity, cost and signal throughput. Promising candidate materials will be incorporated within a multi-layered medium sample. Multi-layered recording, reading, erasure and re-writing will then be experimentally demonstrated.