Holographic data storage materials based on a dye-doped thermoplastic that could find application in professional archival and consumer applications are described. The dye is selected from the class of o-nitrostilbenes, which irreversibly bleaches under exposure to light and shows high thermal stability before and after exposure. The reduction in concentration of the dye in the host after exposure induces refractive index variations over a wide range of wavelengths and extends well away from the dye absorption peak conforming to the Kramers-Kronig relationship. The materials are injection moldable into the standard disc format and have negligible shrinkage during data storage. Samples were produced using different dyes and various concentrations in a polycarbonate host and processed on professional CD/DVD equipment. The refractive index change is as high as 0.04, with a measured instantaneous sensitivity of 0.5 cm/J and M/# = 0.3.
Holographic data storage materials are currently being developed at General Electric. These materials are based on a thermoplastic host doped with narrow-band absorption dyes. The dyes are photosensitive and undergo non-reversible photochromic reactions upon exposure. Samples were produced using different dyes and various concentrations in a polycarbonate host with a focus on sensitivity and capacity of the media. A challenging obstacle for a successful photochromic system is the inherent remaining photosensitivity of the material after the writing process. This paper will introduce the concept of a highly sensitive yet non-volatile photochromic data storage system. The chromophore is subjected to a post-treatment step at a second wavelength which removes the photosensitivity. The stored data can therefore be secured against degradation during read-out at the writing wavelength.
This paper updates the recent progress in the micro-holographic format data recorded in our second-generation dye-doped thermoplastic medium. This new medium is about 400 times more sensitive than our first generation material, while our single-bit system needs less than 2.3 milliseconds to write a micro-hologram. The characteristics of micro-holograms recorded in the high sensitivity material are presented and compared to earlier results from the first-generation low-sensitivity material.
The growing prevalence of digital technologies has led to increased data generation so that new storage technologies must be developed to handle expanding capacity demand. Holographic data storage is a very promising candidate with the potential to provide ultra-high density data storage. Currently, many teams are developing holographic storage technology, with much of the emphasis on professional archival applications. However, consumer-oriented applications are also growing rapidly and the requirements for these applications are different from those for professional archival storage. In particular, a holographic medium for consumer applications must be simple, cheap, and easy to process. In addition, where content distribution is the intended application, the medium must also be compatible with mastering and replication processes. We present a new holographic medium designed to meet the requirements of consumer oriented applications. The media is based on thermoplastic materials that are modified by the inclusion of photo-chemically active dyes. A series of 0.6 and 1.2 mm thick discs were injection molded and characterized for holographic storage capacity and sensitivity. The first series of samples showed large refractive index modulations of 0.03 but a poor sensitivity of 0.1 cm/J. Analysis of the data showed that the low sensitivity limited the usable capacity of the media to M/# values of ~1. A new series of dyes were synthesized with optimized efficiency and injection molded in 1.2 mm substrates. These substrates demonstrated comparable usable capacity but with significantly increased sensitivities. The results of the measurements of the injection-molded thermoplastic media are presented.
A new holographic data storage material based on narrow-band absorption is currently being developed at General Electric. Experimental characterization results of the preliminary materials are presented.
The third order susceptibility of a polydiacetylene polymer was investigated by three different nonlinear spectroscopic techniques in order to test two existing microscopic theories which predict the nonlinear response of such molecular systems. We previously found good agreement between a four essential state model and the THG spectra of (pi) -electron conjugated backbone polymers. However, when such a model was extended to two additional third order susceptibility spectra, poor agreement was found. In contrast the recently developed anharmonic oscillator model fitted well all four experimentally obtained spectra of the third order susceptibility.