Spatially distributed spectral storage.

A new technique for overcoming the effects of excitation-induced frequency shifts in swept-carrier optical memories is proposed and demonstrated. Spectral storage capacity increases of more than 2 orders of magnitude were achieved through implementation of the method.

Data compression in frequency-selective materials using frequency-swept excitation pulses.

We demonstrate the temporal compression of photon echoes in frequency-selective materials by application of frequency-swept excitation pulses. Experimental results in Pr(3+):Y(2)SiO(5) for two- and three-pulse photon echoes are presented and compared with theory. A possible application to temporal reduction of optical data streams is shown.

Recording of 6000 holograms by use of spectral hole burning.

Experiments verifying a new method of storing spectral hole-burning holograms, which yields reduced cross talk as compared with standard spectral hole-burning holograms, have been conducted. Results demonstrating the reduced width of this type of hologram in both frequency and the applied electric-field dimension are presented. Analytic solutions for the spectral width and diffraction efficiency of these holograms are presented. Using this exposure technique, we have recorded 6000 holograms in a single spectral hole-burning sample.

Frequency and phase swept holograms in spectral hole-burning materials.

A new hologram type in spectral hole-burning systems is presented. During exposure, the frequency of narrow-band laser light is swept over a spectral range that corresponds to a few homogeneous linewidths of the spectrally selective recording material. Simultaneously the phase of the hologram is adjusted as a function of frequency-the phase sweep function. Because of the phase-reconstructing properties of holography, this recording technique programs the sample as a spectral amplitude and phase filter. We call this hologram type frequency and phase swept (FPS) holograms. Their properties and applications are summarized, and a straightforward theory is presented that describes all the diffraction phenomena observed to date. Thin FPS holograms show strongly asymmetric diffraction into conjugated diffraction orders, which is an unusual behavior for thin transmission holograms. Investigations demonstrate the advantages of FPS holograms with respect to conventional cw recording techniques in freq ncymultiplexed data storage. By choosing appropriate phase sweep functions, various features of holographic data storage can be optimized. Examples for cross-talk reduction, highest diffraction efficiency, and maximal readout stability are demonstrated. The properties of these FPS hologram types are deduced from theoretical considerations and confirmed by experiments.

Procedure for recording multiple-exposure holograms with equal diffraction efficiency in photorefractive media.

We report experimental results that demonstrate for the first time, to our knowledge, more than 20 holograms stored and recalled with equal diffraction efficiency in photorefractive LiNbO(3). A physical explanation for this new recording procedure is presented, and a comparison is made with previous exposure methods that shows an order-of-magnitude increase in diffraction efficiency with the order of exposure for optically erasable holograms. The procedure holds for recording times much less than the saturation exposure time.