Holographic Storage Characteristics Of SiO₂-nanoparticle/Photopolymer Compound Materials

The excellent photochemical properties of photopolymer material have made them become the hot spot of current research on ultra-high density holographic recording material. However, the shortcomings of common photopolymer materials such as exposure shrinkage and limited refractive index modulation affect the reading and writing properties of their holographic storage. This thesis, built on the theoretical basis of the fact that organic/inorganic composite materials possess the advantages of anti-shrinkage and increasing the refractive index modulation of materials, mainly carries out work on organic/inorganic photopolymer materials blended with SiO₂-nanoparticles from the following aspects:1. The material of acrylimide/polyvinyl alcohol blended with hydrophilic SiO₂-nanoparticles for holographic storage is fabricated. Through improvement on the preparing process of photopolymer film, these SiO₂-nanoparticles are evenly dispersed in the polymer system.2. By testing the refractive index of nanoparticle/polymer composite hologram through Michelson interferometry, it analyzes the distribution of different refractive indexes and proves the counter diffusion exists in the forming process of the grating of nanoparticles and monomer within the sample.3. The holographic properties of the materials under different exposure conditions are studied. By analyzing the parameters of holographic properties, an optimum exposure intensity is found out.4. The polymer samples doped with different density of SiO₂-nanoparticles are prepared. Under the optimum exposure scheme, the bragg-mismatch and shrinkage ratio of all samples is analyzed, combining experimental tests and theories and comes to a conclusion: adding those nanoparticles increases the dimensional stability of the samples during the exposure process. Also, though analyzing the curve of transmittance changing against exposure time, the homogeneity of such photopolymer film is demonstrated.5. The curves of diffraction efficiency, refractive index modulation, exposure sensitivity and other static parameters changing against the density of SiO₂-nanoparticles and exposure time of the samples blended with SiO₂-nanoparticles of different density are tested, and explain the causes of these changes. Finally, it works out an optimum plan of SiO₂-nanoparticles density, which allows all holographic properties to attain the ideal value.