Content-addressable data storage by use of volume holograms.

Data stored as volume holograms--optical interference patterns imprinted into a photosensitive storage material--can be accessed both by address and by content. An optical correlation-based search compares each input query against all stored records simultaneously, a massively parallel but inherently noisy analog process. With data encoding and signal postprocessing we demonstrate a holographic content-addressable data-storage system that searches digital data with high search fidelity.

Experimental evaluation of user capacity in holographic data-storage systems.

An experimental procedure for determining the relation between the number of stored holograms and the raw bit-error rate (BER) (the BER before error correction) of a holographic storage system is described. Compared with conventional recording schedules that equalize the diffraction efficiency, scheduling of recording exposures to achieve a uniform raw BER is shown to improve capacity. The experimentally obtained capacity versus the raw-BER scaling is used to study the effects of modulation and error-correction coding in holographic storage.

Balancing interpixel cross talk and detector noise to optimize areal density in holographic storage systems.

We investigate the effects of interpixel cross talk and detector noise on the areal storage density of holographic data storage. A numerical simulation is used to obtain the bit-error rate (BER) as a function of hologram aperture, pixel fill factors, and additive Gaussian intensity noise. We consider the effect of interpixel cross talk at an output pixel from all possible configurations of its 12 closest-neighbor pixels.

Experimental study of the effects of a six-level phase mask on a digital holographic storage system.

We measure the M/# and the bit-error rate of a digital holographic storage system with a 4f optical arrangement for three configurations: recording at the Fourier plane with and without a phase mask and recording outside the Fourier plane without a phase mask. Unexpectedly, no significant change in the dynamic range was observed when a phase mask was used to record in thick crystals. However, we show that a phase mask is a key component in a 4f digital holographic storage system if high-fidelity holograms with optimum volumetric density are to be stored.

Pixel-matched holographic data storage with megabit pages.

Digital data-page holograms consisting of 1024 x 1024 arrays of binary pixels have been stored and subsequently retrieved with an optical exposure consistent with a data rate 1 Gbit /s. Each input pixel was precisely registered with a single detector pixel, and a raw bit-error rate as low as 2.4 x 10(-6) was demonstrated with global-threshold detection.