| The high demand is placed on data storage technology as the information science and technology has been developed more and more rapidly in the last decade years. The holographic storage is one of the most promising optical storage technologies for high-density dada storage. The ability to store multiple holograms within a small volume of a storage material and to retrieve data pages with thousands of bits in parallel provides an attractive combination of high density and fast speed. While many parts of this technology have made good progress (such as increasing data storage density, reducing access time, improving performances of photorefractive memories, and the like), the volatility of the stored data in photorefractive materials has become serious obstacle to the practical realization of photorefractive holographic memories.In the thesis, the technical process of batch thermal fixing for high-density holographic storage in photorefractive materials has been proposed based on the comparison between the two basic schemes of thermal fixing, post-recording fixing and fixing while recording. The dynamic behaviors of both electrons and irons in the case of light illumination and elevated temperature are analyzed, and hereby the optical erasure effect of subsequent recording light on fixed electronic gratings and the thermal erasure effect of subsequent heating on revealed ionic gratings are presented. According to theoretical model given by A. Yariv, the partial revealing effect of subsequent recording light on fixed holograms has been described, and accordingly inter-batch optical erasure time constant, F, is proposed to evaluate the optical erasure to electronic gratings compensated by ions. The special experiment for measuring the parameter F is designed and performed. The experimental result shows that inter-batch optical erasure time constant, F, is much longer than intra-batch optical erasure time constant, E, which agrees well with the theoretical prediction. Furthermore, the exposure schedule for recording holograms with equalized diffraction efficiency is designed based on the above-mentioned optical erasure time constants.The parameter M#max_balch termed as dynamic range with maximum number ofbatches, is defined for quantitatively characterizing the enhancement in storagecapacity of batch thermal-fixing scheme for multiple holographic storage. Another parameter, M#ejf, termed as effective dynamic range is proposed to evaluate system'sstorage ability, and hereby the effective dynamic range values corresponding to the number of batches are calculated and compared. The calculation result shows that, by using single fixing for multiple storage, the storage capability declines inevitably as nonvolatile storage has been realized. However, enhancing nonvolatile storage capability of a given storage system is possible by using batch thermal fixing scheme with a proper number of batches. And then, the method for determining the optimum number of batches for fixing a given number of holograms is present based on above research.The diffraction efficiencies of multiple holograms recorded and fixed in different number of batches are calculated and analyzed. If a special exposure schedules calculated based on the characteristic time constants of batch fixing scheme is incorporated for equalized diffraction efficiency, the greater the number of batches is, the higher the equalized diffraction efficiency of fixed holograms. Owing to the batch-fixing scheme, the exposure time for recording individual hologram is more uniform and the total exposure time is short than that by using single-fixing scheme. Therefore, the noise such as crystal scattering due to long exposure time can be suppressed, and storage capability and fidelity can be improved.The high-density holographic storage system, including on-line and off-line heating units, has been designed and implemented for our experiments. This system can be used to store no less than 10000 holograms, and it is flexible and practical to operate.
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