A New Optical Method of Storing and Retrieving Information

Data storage based on photochromic and photoconvertible fluorescent proteins

“…This latter point is crucial if one intends to address a particular volume of optically encoded information (voxel) within a three-dimensional matrix in order to encode more data than on a surface. For transparent materials, three-dimensional optical encoding was pioneered by the invention of holographic data storage (van Heerden, 1963), relying on the recording of interference patterns within a thick photosensitive material. It opened the way to the development of irreversible (Chen et al, 1968) and reversible (von der Linde and Glass, 1975) three-dimensional optical encoding techniques on various substrates such as mineral crystals (Andersen and Marrakchi, 1994;Heanue et al, 1996;Bai et al, 1997), glass (Cheben and Calvo, 2001), liquid crystals (Jang and Shin, 2001) or plastic polymers (Dubois et al, 2005;Sheridan et al, 2007).…”

Holographic random access memory (HRAM)

“…When the hologram is subsequently illuminated with one of the original reference beams, light is diffracted from the grating in such a way that the signal beam is reproduced. Many holograms can be multiplexed within the same volume of the material by angle [6], [7], fractal [8], wavelength [9], [10], phase code [11]- [13], peristrophic [14], and shift [15], [16] multiplexings.…”

Features of representing the information content of holograms in terms of optical degrees of freedom

“…This also refers to the case of volume holo grams. According to van Heerden [5], the limiting density of data recording in this case is I 3D = (V/λ 3 )log 2 ψ, where V is the volume of the recording medium and λ is the light wavelength. For λ = 0.63 μm, the density of data recording is 10 13 bit/cm 3 , The corresponding number of the degrees of freedom can be estimated as V/λ 3 .…”

“…The informational capacity of recon structed holograms and the corresponding number of degrees of freedom are arithmetically added (similarly to the case of synthesized aperture). As a result, it might be possible to achieve an informational capacity exceeding that given by the van Heerden formula [5], if there were no restrictions imposed by some proper ties of the recording medium, primarily by its spatial resolution. Other limiting factors include noises and the dynamic range of the medium in which the set of holograms is recorded, as well as the scattering due to which the signals recorded in different regions and intervals are not fully independent.…”