Content-addressable holographic databases

Holographic data storage allows the simultaneous search of an entire database by performing multiple optical correlations between stored data pages and a search argument [1,2]. We have recently developed fuzzy encoding techniques for this fast parallel search and demonstrated a holographic data storage system that searches digital data records with high fidelity [2]. This content–addressable retrieval is based on the ability to take the two– dimensional inner product between the search page and each stored data page. We show that this ability is lost when the correlator is defocussed to avoid material oversaturation [3], but can be regained by the combination of a random phase mask and beam confinement through total internal reflection. Finally, we propose an architecture in which spatially multiplexed holograms are distributed along the path of the search beam, allowing parallel search of large databases.