Photopolymers are special polymeric materials that can be irradiated with light to form polymer structures. It is widely used in the fields of 3D printing, anti-counterfeiting and information storage. In today's relatively mature holographic storage technology, high-density volume holographic data storage requires storage materials with a high response rate, high effective storage density and optical transparency, and high signal-to-noise ratio, etc. For this reason, storage materials have been studied in various fields. Phenanthrenequinone (PQ)/poly(methyl methacrylate) (PMMA) materials are a choice for holographic storage. By modifying the polymer substrate of the lamellar PQ/PMMA holographic polymeric material, it is possible to reduce the generation of bubbles during the preparation of the material to increase the usable area of the material, and at the same time, it is also possible to improve the photoreceptor sensitivity to a certain extent, to increase the read/write speed of the material and to analyze the causes of the phenomenon using the first nature principle calculations.
Phenanthraquinone-doped polymethyl methacrylate (PQ/PMMA) photopolymers with excellent characteristics of simplicity for manufacture, negligible photo-induced volume shrinkage, low cost, and high resolution for holographic data storage. In this paper, we explored the phenomenon of different PQ concentrations of PQ/PMMA photopolymers on collinear holography system. By designing a set of control experiments with different PQ doping ratios of 0.5%, 0.7%, 0.9%, 1% and 1.1% (1% means the ratio of monomer, thermal-initiator and photo-initiator are Methyl methacrylate:2,2'- Azobis(2-methylpropionitrile): PQ=100:1:1). And the Bit Error Rate (BER) of the reconstructed image using different PQ/PMMA photopolymers were measured, and we found that, at the value of the BER of 0.05, the material of 1% PQ/PMMA can last a longer time than other different PQ concentrations from 0.5% to 0.9% of PQ/PMMA at a recording beam intensity exposure. The 1.1% PQ/PMMA and the 1% PQ/PMMA can achieve the BER of 0.05 at the same time, but the 1.1% PQ/PMMA only last half time of the 1% PQ/PMMA. Furthermore, the diffraction efficiency has an obvious increase with the increase of the PQ concentrations from 0.5% to 1.0% of PQ/PMMA (from 10% to 60%), while it tends to decrease as the PQ concentration continues to increase to 1.1% due to the poor solubility. In summary, from the BER and holographic grating diffraction efficiency result, we got the optimal concentration of PQ in the PQ/PMMA photopolymer is 1%, and the current study is very meaningful for the use of PQ/PMMA in collinear holography data storage.
Polarization holography based on tensor theory can accurately describe the reconstruction characteristics at arbitrary interference angles, so some optical elements such as wave plates can be produced by polarization holography. The wave plates are important optical elements that can control the phase and polarization state of wave. Conventional wave plates convert the polarization state of the incident wave through crystal birefringence and then require the accurate thickness. Based on the polarization holography described by tensor theory, we produce the half-wave plate whose azimuthal angle of fast axis may be arbitrary by using the polarization sensitive material, phenanthrenequinone-doped poly methyl methacrylate (PQ/PMMA).
Phenanthraquinone-doped polymethylmethacrylate (PQ/PMMA) photopolymer is a promising material for holographic data storage, according to the negligible shrinkage, polarization sensitivity, and easy preparation. In this paper, we investigated the effect of thermal polymerization temperature and time of PQ/PMMA on the collinear holographic data storage system. By designing the baking temperatures 50℃ and 60℃ and baking times 4-20 hours each 2 hours during thermal polymerization. The information page storage and representation results show that under the baking temperature of 50℃ when the baking times were less than 8 hours, the material could not record the data page, and the bit error rate (BER) of the reconstructed data page was increased with the baking time extension. The material baked for 10 hours recorded data with the best results and reconstructed data pages with a minimum BER of 1.5%, when the baking time is 20 hours, the BER of the reconstructed data page was increased by about 12% compared to the baking time of 10 hours. When the baking temperature is 60℃, the data page BER was also increased with the baking time extension except for a very short baking time within 2.5 hours. We analyze the molecular weight of these materials that can be changed by controlling the baking temperature and time of thermal polymerization properly so that grating generation and readout efficiency can be changed. We believe the analysis is useful for the application of PQ/PMMA on collinear holographic data storage.
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)
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