We describe a digital holographic storage system for the study of noise sources and the evaluation of modulation and error-correction codes. A precision zoom lens and Fourier transform optics provide pixel-to-pixel matching between any input spatial light modulator and output CCD array over magnifications from 0.8 to 3. Holograms are angle multiplexed in LiNbO(3):Fe by use of the 90 degrees geometry, and reconstructions are detected with a 60-frame/s CCD camera. Modulation codes developed on this platform permit image transmission down to signal levels of ~2000 photons per ON camera pixel, at raw bit-error rates (BER's) of better than 10(-5). Using an 8-12-pixel modulation code, we have stored and retrieved 1200 holograms (each with 45,600 user bits) without error, for a raw BER of <2x10(-8).

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. To our knowledge, this is the first demonstration of the often-cited goal of holographic data storage of megabit data pages and a gigabit-per-second data rate.

Two novel techniques for eliminating deterministic noise from a page-oriented memory are presented. The first technique equalizes the output response of ON pixels by adjustment of the exposure of each pixel during the recording of each data page. A test image transmitted through the system measures the spatial nonuniformities, and the appropriate inverse filter is imposed upon the data page and recorded in the storage material. On readout, the output signal values are then spatially uniform, perturbed only by random noise sources. Experimental results of using this predistortion technique in a pixel-matched holographic storage system are shown. Under conditions of high volumetric density, raw bit-error-rate (BER) improvements of 6-8 orders of magnitude are obtained (from 10(-4) to <10(-10)). The second technique uses a phase shift during holographic storage to subtract from bright OFF pixels. Under conditions of low spatial light modulator contrast, BER improvements of 6 orders of magnitude (from 10(-2) to 10(-8)) are demonstrated.

Broadband detection (150-MHz range) of surface acoustic wave transients excited by absorption of ps laser pulses in the sample under study is demonstrated. A novel transducer employing a ferroelectric polymer foil as piezoelectric sensor is described. In a silicon single crystal the width of the observed acoustic pulses was limited to 4 ns by the spatial resolution of pulse generation and detection. In the polycrystalline materials under study the minimum observable pulse width was determined by materials properties. Accurate values for the phase velocity of surface acoustic wave propagation are given for silicon, aluminum, steel, copper, and brass.

The design and the realization of an advanced precision optical test stand for evaluating materials and developing tools and techniques for holographic digital data storage are described. This apparatus allows studies of holographic recording materials and recording physics to be performed in the context of practical data storage. The system concept, its implementation, and its performance are described, and examples of holographic storage in photorefractive materials are discussed.