Photopolymers are considered to be the most potential holographic storage materials due to their advantages of high resolution, real-time recording and low-cost preparation. Thereinto, Phenanthraquinone-doped polymethyl methacrylate (PQ/PMMA) photopolymers have excellent properties such as easy to prepare, controllable thickness, negligible photoinduced volume shrinkage, and long life-time for holographic data storage. Nevertheless, the current holographic properties such as diffraction efficiency and photosensitivity of PQ/PMMA photopolymers cannot meet the requirements of the information writing-speed. It is well known that the holographic properties of materials can be improved by optimizing preparation conditions and doping nanoparticles. The concentration of PQ can increased to 1.0 wt.% using 60 °C as the prepolymerization temperature in our previous report. Herein, via introducing a new monomer pentaerythritol-tetrakis-3-mercaptopropionate (PETMP) into PQ/PMMA, the photosensitizer concentration of PQ could be increased to 2.0 wt.% compared with PQ/PMMA. And under the same production process conditions, both of the photosensitivity and diffraction efficiency of PETMP-PQ/PMMA increased ~20 times (from ∼0.27 cm/J to ∼5.61 cm/J) and more than 25% (from ~50% to ∼75%). Finally, by the use of the PETMP−PMMA/PQ in a collinear holography system, it appeared to be promising for a fast but low bit error rate(BER) in holographic information storage. The current study shows that, PETMP-PQ/PMMA material has the excellent potential for holographic data storage. Keywords: Photopolymer, PQ concentration, photosensitivity, co-monomer
There are many ways to realize null reconstruction in polarization holography, which can be divided into two types. One is the null reconstruction without exposure response coefficient constraint, and the other is the null reconstruction limited by the exposure response coefficient. On the basis of previous studies, we have further studied these two types of null reconstruction, and obtained the necessary conditions for realizing the two types of null reconstruction under arbitrary interference angle and polarization state.
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 has gained traction with the development of tensor theory. It primarily focuses on the interaction between polarization waves and photosensitive materials. By introducing the polarization characteristics of light into conventional holography, more degrees of freedom can be provided to control optical information. Based on the polarization modulation of polarization hologram, we propose a method to realize bifocal-polarization holographic lens in volume hologram. Two foci can be generated simultaneously or separately by changing the polarization state of the reading wave. The material used is a PQ/PMMA polarization sensitive medium, the thickness is 1.5mm. The bifocal-polarization holographic lens has 112 mm clear aperture and 446mm focal length.
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.
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