Digital Holographic Data Storage In Photopolymer Materials

Owing to its attractive combination of capacity and transfer rate, volume holographic storage (VHS) is treated as the promising next generation data storage technology. The potential applications of VHS include a variety of fields such as information processing, aviation and spaceflight, national defense security, photopolymers have been considered as the most promising material for mass holographic storage. Although VHS technology has got great achievement at many aspects in recent years, and the holographic digital data storage technology has been progressing rapidly, the experimental demonstration of holographic digital data storage in photopolymers has been presented as well, there is hardly such research report in our country. This thesis focuses on the study of realization of large size data page, high-fidelity digital data storage in photopolymer media, on the basis of the previous work of our research group.This thesis introduces the fundamental principles of VHS first, and summarizes the evaluation method of data fidelity of holographic pages. Then the scattering noise of photopolymer is deeply investigated by means of Loss of Signal-to-Noise Ratio (LSNR). We accomplished the measurement of many series of photopolymer samples provided by Technical Institute of Physics and Chemistry of Chinese Academy of Science, and selected some media with less noise which are suitable for the experiments of digital holographic data storage. By analyzing the results of LSNR measurements for samples with different components, and comparing with the media of Aprilis Corporation, we give the suggestion to optimize the material components in the future.In addition, based on the physical mechanism of intra-page crosstalk noise, we proposed the Pixel-Matched Spread Function (PMSF), and a simplified deconvolution arithmetic to suppress the intra-page crosstalk noise. Both the computer simulation and the experimental results showed that this PMSF arithmetic can suppress the intra-page crosstalk noise soundly, thus improve the fidelity of retrieved data page.Finally, from the view point of recording high-fidelity data page, we optimized the storage system by using beam shaper in signal beam, and redesigning geometry to increase the uniformity of reference beam. In the final demonstration experiment, we encode 10KB Flash to four data pages, each including 512×512 bits. The data pages are 1:2 pixels matched. These four data pages were stored in a single point in a photopolymer media of Aprilis Corporation by using angle multiplexing method, and successfully retrieved. The average raw BER of retrieved data pages after shift-compensation and PMSF algorithm reached 2.4×10-4.To our knowledge, the results presented in this thesis are the first demonstration of holographic multiplexing recording and retrieval of high fidelity digital data pages which contain as much as 512×512 pixels in photopolymer media in our country.