Materials and systems for two photon 3-D ROM devices

Abstract

The methods and systems used for storing and accessing information in three dimensions by means of two-photon absorption are described. The materials into which the information is stored are organic molecules dispersed in polymer matrices, which change structure and spectra after absorption of light. The writing and accessing of the information can be performed either bit-by-bit or in a two-dimensional (2-D) multibit plane format. Automated recording and readout three-dimensional (3-D) systems have been constructed and characterized. Channel error sources have been identified, and a custom spatial bit-errorrate test has been developed.

Nonvolatile read-out molecular memory

“…V olumetric optical storage by means of two-photon absorption was first proposed in 1989 (1)(2)(3). Ever since then the goal has been to design and synthesize materials that are suitable for terabyte removable-storage devices.…”

“…Such 3D volumetric storage devices will satisfy a large number of the storage requirements imposed by telemedicine, high-definition movies, defense, and other applications. Prototype, removable volumetric storage devices have been designed and fabricated commercially (2); however, thus far these have been limited to read-only memory (ROM) and write once read many (WORM). Rewritable optical-storage devices of this type have been hindered by the absence of materials that are capable of erasing and of nondestructive read-outs.…”

Multilayer optical storage disk based on the frequency up-conversion effect from rare-earth ions

“…To overcome this problem, an approach based on the use of the multiphoton excitation effect has been reported by several authors. [1][2][3] In the multiphoton excitation process, since the excitation rate is proportional to the square or higher order of the incident intensity, the resolution of the data bits and the level of interlayer crosstalk are greatly improved.…”

Two-wavelength holographic recording in thick phenanthrenequinone-doped poly(methyl methacrylate) photopolymer

“…It may be able to open a new window for photopolymer on different applications of optical information, such as data storage, communication, and holographic imaging. [3][4][5] The first demonstration of two-wavelength holography in photopolymer was made by Bjorklund et al in 1981, 1 who proposed to utilize a photosensitive dye with four-level energy schemes with cascade-excited metastable intermediate levels for performing two-wavelength recording. They successfully demonstrated holographic recording in a 200 μm thick carbazole dissolved in PMMA thin film.…”

“…[1][2][3][4][5] The features include the ability to record holograms with low-intensity and/or longerwavelength lasers, nondestructive readout before the recording medium reaches saturation, as well as the ability to do selective recording by gating the sensitivity of the medium optically. If these features were combined with volume holography, one could have more freedom for designing optical systems and/or creating innovative ideas for applications.…”