Low-Cost Optical Search of Digital Holographic Data Storage System

Digital holographic data storage systems currently under development have Terabit storage capacity, as is necessary for the next generation of huge entertainment and business databases. However, even at Gbit/second transfer rates, each search of such a database for a particular item will take a minimum of a quarter of an hour of dedicated, high-speed computing time. In contrast, an all-optical search can be performed in milliseconds, independent of the size of the database. This proposal presents a design which is capable of complex searches of a Gbit of holographically sotred digital data in a msec. While the properties of image-based (analog) volume holographic correlators are known, associative search/correlation of digital folume holographic data present unique problems and opportunities because of the spatially-varying digital data encoding. The choice of optical impmlementation, digital channel encoding, error-correction technique, and data page layout all effect the bit-error-rate, cross correlation suppression, level of association and generalization, and degree and type of shift-invariance of the search engine. The design presented in this proposal maximizes digital search capabilities, and can be added to holographic memory architectures at extremely low additional cost.