Jian Wang,Jian Wang,YanBo Pei,Hongyan Shi,Bo Gao,Suhua Luo
We reveal that polymerization degree is a significant factor that affects the holographic properties of glass-like photopolymer. By modulating polymerization degree, as well as changing the photosensitizer concentration, we fabricate multilayer PQ/PMMA photopolymer, exhibiting excellent performances in storage fidelity and reproduction resolution. A reflection geometry holographic disk system is established using the multilayer sample, in which a high storage density of 40.5GB/cm3 is realized. The reproduced images exhibit high quality with an average diffraction efficiency of 7.4 × 10−4 and average peak SNR of 27.4. This study provides a paradigm for the fabrication and holographic application of other photopolymers.
Photopolymer is well-recognized as an ideal holographic data storage medium. In order to improve the holographic performance of a two-stage photopolymer, five acrylate dendritic monomers ( DM-1/2/3/4/5 ) with high refractive indices (1.590–1.634) are designed and synthesized in this study. Their structures are characterized by 1 H NMR, 13 C NMR, FTIR and HR-MS spectra, and their photopolymerization kinetics are investigated through real-time FTIR. Using these DMs as one recording monomer, a series of photopolymer samples with different formulations are fabricated. The influence of DM-1/2/3/4/5 on the holographic performances of these samples are explored under holographic exposure of a 532 nm laser. The results show that the photosensitivity and angle selectivity of these samples can be improved by adding these DMs. The most excellent holographic characteristics are obtained by a sample with 4% DM-1 . Using it as a data storage medium, a volume holographic grating with high diffraction efficiency of 90% and narrow selection angle of 0.11° is recorded. Moreover, the sample achieves a high dynamic range of 13.7 and a low volume shrinkage of 0.36% after recording 60 holograms through angular-multiplexing with low record/read exposure dose, indicating its great application potential in holographic data storage.
The sync-angular multiplexing by rotating medium is a simple but seldom used technique in recent years. While compared with the regular angular multiplexing, sync-angular multiplexing has the advantage to alleviate the cumulative scattering noise during recording in thick materials. Based on the experimental parameters, the available rotational angle range and spatial selectivity are studied by simulating the recording spot. Experimentally, 150 grey images are sync-angular multiplexed in a 2.0 mm thick PQ/PMMA photopolymer, resulting in an average diffraction efficiency of 0.05% and a storage density of 41.1 GB/cm 3 .
Phenanthrenequinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymers are potential holographic storage media owing to their high-density storage capacities, low costs, high stability, and negligible shrinkage in volume holographic permanent memory. However, because of the limitations of the substrate, conventional Plexiglas materials do not exhibit a good performance in terms of photosensitivity and molding. In this study, the crosslinked structure of PMMA was modified by introducing a dendrimer monomer, pentaerythritol tetraacrylate (PETA), which increases the photosensitivity of the material 2 times (from ~0.58 cm/J to ~1.18 cm/J), and the diffraction efficiency is increased 1.6 times (from ~50% to ~80%). In addition, the modified material has a superior ability to mold compared to conventional materials. Moreover, the holographic performance enhancement was evaluated in conjunction with a quantum chemical analysis. The doping of PETA resulted in an overall decrease in the energy required for the reaction system of the material, and the activation energy decreased by ~0.5 KJ/mol in the photoreaction stage.
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