Exponential growth of data motivates scientists to develop novel optical data storage technologies with the merits of low cost, large capacity, long lifetime, and low power consumption, thus facilitates the development of low-carbon and environmentally friendly economy. Volume holographic data storage, as a promising new generation optical data storage technology, has attracted a tremendous amount of attention within the scientific community, and the lack of appropriate storage medium seriously hinder its large-scale commercial applications. PQ/PMMA photopolymers possess excellent characteristics of low cost, neglectable volume shrinkage and controllable thickness for holographic data storage, while poor holographic performance inhibits its direct applications. Herein, via simply introducing C60 nanoparticles in PQ/PMMA, we successfully synthesize photopolymer with a record-high diffraction efficiency and refractive index modulation, for the first time, reaching up to ~80% and ~1.13×10-4, respectively. More interestingly, C60 nanoparticles here dramatically enhance the intensity holography, but seriously suppress the polarized holographic one. Experimental characterizations and theoretical simulations demonstrate that polarization sensitive holographic performance and reduction of photoinduced anisotropy induced by C60 stem from the strong π-π non-bonding interactions between PQ photosensitizers and C60 molecules (supramolecular) but not chemical reactions. Moreover, C60-PQ/PMMA show a great potential for holographic data storage, exhibiting high chemical stability under extreme working conditions and the angle-multiplexing of 321 gratings and corresponding holographic images are successfully recorded and read on it.
Acknowledgment: This work was financially supported by the National Key R&D Program of China (Grant NO. 2018YFA0701800)
Based on tensor polarization holography, the variation of exposure response coefficient with the increase of exposure energy under different recording process is introduced in this paper. We find that different recording processes have different effects on the exposure response coefficient. However, at the beginning of exposure, there is an initial value of the exposure response coefficient independent of the holographic recording process. With this special phenomenon, polarization modulation of reconstructed wave can be easily realized at low exposure energy, such as faithful reconstruction, orthogonal reconstruction and null reconstruction.
The holographic performance of photo-polymeric material PQ/PMMA is found to be largely determined by pre-polymerization modulation, such as stirring time and pre-polymerization temperature, during the material preparation process. In the current study, in order to determine the best stirring time during the pre-polymerization process, the influence of stirring time on the holographic properties of PQ/PMMA here is seriously analyzed. Experimental observations clearly indicate that, under the same baking conditions, the diffraction efficiency of PQ/PMMA increase initially with the stirring time but then decrease as the stirring time continue increases. When the stirring time is 75 min, the holographic performance of PQ/PMMA reaches its best in which the diffraction efficiency of the material can reach up to 49.3%. Current study here determines the optimal stirring time and pre-polymerization temperature during the pre-polymerization process, thus provide an effective guidance for further preparation of PQ/PMMA photo-polymer materials with excellent holographic properties.
In polarization holography, the polarization information is recorded in the photopolymer material by interference, and the polarization state of the reconstructed wave can be calculated accurately by tensor method. Based on the guidance of tensor theory, this paper systematically analyzes the method of faithful reconstruction under any interference angle independent of exposure energy, and gives experimental verification under the condition of 40° interference angle. This conclusion is helpful to broaden our understanding of polarization holography based on tensor theory, and can be applied to the research of polarization multiplexing multi-channel holography.
The concentration of photosen-sitizer is an important factor affecting the properties of holographic materials. Most researchers use doping or copolymerization methods to increase the saturation dissolvability of photo-sensitizer. However, the addition of multiple components will reduce the molecular mass of the photoproducts and the polymer substrate, resulting in poor stability of the grating. In this paper, we studied the solubility of phenanthraquinone (PQ) in MMA at different temperatures. At 60 °C, the solubility of PQ could reach 1.8%. Meanwhile, we found that the thermo-initiator concentration of 2,2-Azobis(AIBN) affected long-chain carbon polymerization. Therefore, proper concentration balance has a huge impact on the performance of the materials. Finally, we obtained a relatively suitable concentration balance of PQ/PMMA photopolymer, making it more suitable for volume holographic data storage.
This paper focuses on the causes of bubbles in the fabrication of holographic storage materials phenan- threnequinone(PQ)/polymethyl methacrylate(PMMA).Three main possibilities for generating bubbles are proposed.Azodiisobutyronitrile(AIBN) decomposes to generate nitrogen,which cannot diffuse to generate bubbles.The temperature is too high,and the local boiling of methyl methacrylate(MMA) produces bub- bles.Bubbles caused by changes in material volume.Simulation and experimental verification of the three cases show that the main reason for the generation of bubbles is the sudden shrinkage of the material.It is determined that the temperature is the second in uencing factor.
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