Significant Enhancement of the Polarization Holographic Performance of Photopolymeric Materials by Introducing Graphene Oxide

Focused polarization hologram with arbitrary polarization to a specified polarization conversion

Polarization devices play a key role in many optical technologies and applications. However, traditional polarization devices are often large and lack integration, and achieving polarization conversion typically requires combining multiple devices, which makes it challenging to realize integrated optical systems. Following the current trend of optical devices, we propose a method using polarization holographic exposure to prepare polarization conversion devices. This approach allows for the fabrication of devices that can convert arbitrary polarization states into specified polarization states while also incorporating a focusing function. Specifically, two types of polarization conversion holograms are fabricated. One is a linear polarizer with a focusing function, and the other is a circular polarizer with a focusing function. Their polarization extinction ratio is around 35 dB, which has a certain competitiveness in similar devices. This method simplifies the preparation process of multifunctional polarizing devices while ensuring their performance. Our work has potential applications in the fields such as polarization emission, imaging, and sensing. Additionally, this approach broadens the design concept of polarization conversion devices, which may promote the development of optical devices with lower cost and higher integration.

Organocatalytic Enantioselective Friedel-Crafts Reaction of Phenanthrenequinones and Indoles

An efficient stereoselective synthesis of 10-hydroxy-10-(1H-indol-3-yl)-9-(10H)-phenanthrene derivatives was realized through an organocatalyzed Friedel-Crafts reaction of phenanthrenequinones and indoles using a (S,S)-dimethylaminocyclohexyl-squaramide as the catalyst. Under the optimized conditions, the desired chiral products were obtained in good yields (73-90%) with moderate to high ee values (up to 97% ee). Two pairs of synthesized enantiomers were subjected to evaluation of their antiproliferative activities on four types of human cancer cell lines and one human umbilical vein endothelial cell line using the CCK-8 assay. The results indicated that stereoselectivity had obvious impacts on biological activity. (S)-4g was found to have optimal cytotoxicity against the A549 cell line and a good safety profile for human normal cells, which was better than the inhibitory activity of the positive control drug (doxorubicin).

Strategy for Simple Control of High Performance PQ/PMMA Holographic Media

Holographic data storage technology is a cost-effective solution for long-term archival data storage. However, the development of suitable holographic recording materials remains a challenge. Among these materials, phenanthraquinone-doped poly(methyl methacrylate) (PQ/PMMA) stands out due to its low cost and controllable thickness. Nevertheless, its limited photosensitivity and diffraction efficiency hinder its widespread application. In order to solve these problems, we put forward a kind of convenient and simple, low cost strategy, by adding plasticizer N,N-dimethylformamide (DMF) for preparation of DMF-PQ/PMMA photopolymer, avoid the use of complex compounds. The addition of DMF not only influences the thermal polymerization stage but also forms weak interactions with PQ during the photoreaction process, thereby enhancing the holographic performance of DMF-PQ/PMMA. Consequently, we achieved a remarkable 9.1-fold increase in photosensitivity (from ∼0.35 to 3.18 cm J-1), improved diffraction efficiency by 20% (from 65% to 80%), and reduced volume shrinkage by a factor of 8 (from 0.4% to 0.05%). Furthermore, utilizing a collinear holographic storage system with multiplexing shift at a scale of 5 μm resulted in an impressively low minimum bit error rate (BER) of only 0.36% (with an average BER of 1.4%), highlighting the fast processing capability and potential for low BER applications in holographic information storage using DMF-PQ/PMMA.

Sensitivity-Enhancing Modified Holographic Photopolymer of PQ/PMMA

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.

Polarization evolution on higher and hybrid-order Poincaré spheres with coaxial polarization holograms

Based on the tensor polarization holography theory, we propose a simple and convenient method in the recording material, phenanthrenequinone-doped polymethylmethacrylate, to generate beams on higher and hybrid-order Poincaré spheres, and realize their polarization evolution on the spheres by combining the recorded phase with the Pancharatnam-Berry phase. By simultaneously adjusting the polarization azimuth angle and relative phase of the recorded waves, independent phase-shifts can be imparted onto two orthogonal circular polarization states in reconstruction process of polarization holography. The beams on basic Poincaré sphere are transformed into that on arbitrary higher or hybrid-order Poincaré spheres. We get the Poincaré spheres' type and polarization distribution of the reconstructed wave by interferometry and polarizer, and the results match well with the theoretical predictions.

Highly sensitive and repeatable recording photopolymer for holographic data storage containing N-methylpyrrolidone

The low photosensitivity of phenanthraquinone-doped poly(methyl methacrylate) (PQ/PMMA) severely limits its recording speed for holographic data storage. A high-performance holographic recording medium based on a unique combination of N-methylpyrrolidone (NMP) regulated PQ/PMMA has been developed. A NMP-PQ/PMMA photopolymer with high sensitivity, high diffraction efficiency and negligible volume shrinkage was successfully fabricated by tuning the composition of the PMMA matrix by varying the ratio of NMP to monomers. The photosensitivity is increased by 6.9 times (from 0.27 cm J-1 to 1.86 cm J-1), the diffraction efficiency is increased from 60% to > 80%, and volume shrinkage is decreased by a factor of 2 (from 0.4% to 0.2%). Further investigation revealed that the addition of NMP significantly reduced the molecular weight of PMMA and increased the amount of MMA residuals, while also improving the solubility of PQ molecules. More interestingly, for the first time, the NMP-PQ/PMMA material could record data information repeatedly at least 6 times. The present study elucidates that the introduction of NMP not only modulates the molecular weight of PMMA but also enables the residual monomer MMA to more easily combine with PQ to form a photoproduct for improved holographic performance.

Enhanced Polarization Properties of Holographic Storage Materials Based on RGO Size Effect

Polarized holographic properties play an important role in the holographic data storage of traditional organic recording materials. In this study, reduced graphene oxide (RGO) was introduced into a phenanthraquinone-doped polymethylmethacrylate (PQ/PMMA) photopolymer to effectively improve the orthogonal polarization holographic properties of the material. Importantly, the lateral size of RGO nanosheets has an important influence on the polymerization of MMA monomers. To some extent, a larger RGO diameter is more conducive to promoting the polymerization of MMA monomers and can induce more PMMA polymers to be grafted on its surface, thus obtaining a higher PMMA molecular weight. However, too large of a RGO will lead to too much grafting of the PMMA chain to shorten the length of a single PMMA chain, which will lead to the degradation of PQ/PMMA holographic performance. Compared with the original PQ/PMMA, the diffraction efficiency of the RGO-doped PQ/PMMA photopolymer can reach more than 11.4% (more than 3.5 times higher than the original PQ/PMMA), and its photosensitivity is significantly improved by 4.6 times. This study successfully synthesized RGO-doped PQ/PMMA high-performance photopolymer functional materials for multi-dimensional holographic storage by introducing RGO nanoparticles. Furthermore, the polarization holographic properties of PQ/PMMA photopolymer materials can be further accurately improved to a new level.

Holographic Properties of Irgacure 784/PMMA Photopolymer Doped with SiO2 Nanoparticles

To enhance the holographic properties, one of the main methods is increasing the solubility of the photosensitizer and modifying the components to improve the modulation of the refractive index in the photopolymer. This study provides evidence, through the introduction of a mutual diffusion model, that the incorporation of SiO2 nanoparticles in photopolymers can effectively enhance the degree of refractive index modulation, consequently achieving the objective of improving the holographic performance of the materials. Different concentrations of SiO2 nanoparticles have been introduced into highly soluble photosensitizer Irgacure 784 (solubility up to 10wt%)-doped poly-methyl methacrylate (Irgacure 784/PMMA) photopolymers. Holographic measurement experiments have been performed on the prepared samples, and the experiments have demonstrated that the Irgacure 784/PMMA photopolymer doped with 1.0 × 10-3wt% SiO2 nanoparticles exhibits the highest diffraction efficiency (74.5%), representing an approximate 30% increase in diffraction efficiency as compared to an undoped photopolymer. Finally, we have successfully achieved the recording of real objects on SiO2/Irgacure 784/PMMA photopolymers, demonstrated by the SiO2/Irgacure 784/PMMA photopolymer material prepared in this study, which exhibits promising characteristics for holographic storage applications. The strategy of doping nanoparticles (Nps) in Irgacure 784/PMMA photopolymers has also provided a new approach for achieving high-capacity holographic storage in the future.

Scalar vortex beams produced by Pancharatnam-Berry phase optical elements that utilize polarization holography

We discuss the appearance of the Pancharatnam-Berry phase in polarization holography, and confirm the possibility of generating scalar vortex beams by using the Pancharatnam-Berry phase. The polarization holograms used to generate scalar vortex beams are produced in phenanthrenequinone-doped polymethylmethacrylate (PQ/PMMA), where each radial direction consists of an equivalent half-wave plate hologram with gradually changing directions. The spin angular momentum carried by a circular polarization reading wave is converted into orbital angular momentum in a reconstruction process, resulting in the formation of scalar vortex beams with positive and negative topological charges controlled by the reading polarization.

Generation of vector beams based on diffraction characteristics of a linear polarization hologram in coaxial recording

Polarization holography is an effective tool for realizing light field manipulation and can be utilized to generate vector beams. Based on the diffraction characteristics of a linear polarization hologram in coaxial recording, an approach for generating arbitrary vector beams is proposed. Unlike the previous methods for generating vector beams, in this work, it is independent of faithful reconstruction effect and the arbitrary linear polarization waves can be used as reading waves. The desired generalized vector beam polarization patterns can be adjusted by changing the polarized direction angle of the reading wave. Therefore, it is more flexible than the previously reported methods in generating vector beams. The experimental results are consistent with the theoretical prediction.

Circular polarization detector based on polarization holography

We propose and experimentally demonstrate the generation of a circular polarization detector based on planar polarization holography. The detector is designed by constructing the interference field according to the null reconstruction effect. We create multiplexed holograms, which feature the combination of two sets of hologram patterns and operate with opposite circular polarization beams. In a few seconds, the exposure operation allows the polarization multiplexed hologram element to be generated, with functionality equivalent to a chiral hologram. We have theoretically analyzed the feasibility of our scheme and experimentally demonstrated that the right- and left-handed circularly polarized beam can be distinguished directly depending on the different output signals. This work provides a time-saving and cost-effective alternative approach for generating a circular polarization detector and opens avenues for future applications in polarization detection.

Highly sensitive photopolymer for holographic data storage

The insufficient photosensitivity of conventional organic recording materials such as phenanthraquinone-doped poly(methyl methacrylate) (PQ/PMMA) significantly limits the recording speed in holographic data storage. Accelerating the formation of free radicals using the photosensitizer PQ during the photoreaction process and increasing the C = C double bond concentration of the matrix are effective methods for improving the photosensitivity. Using the above methods, we doped PQ/PMMA with the co-photoinitiator triethanolamine and co-monomer acrylamide to improve the photosensitivity of the material. Compared with the original PQ/PMMA material, the photosensitivity was increased by 10 times, and the diffraction efficiency was increased by 20%. The role of each doping component was studied by characterization and analysis. In addition, the introduction of the cross-linking agent N,N'-methylene-bisacrylamide, having high sensitivity, reduced the shrinkage of the material. We verified the application of the new material in a collinear system, and its high sensitivity showed its great potential for holographic data storage.

Phenanthraquinone-Doped Polymethyl Methacrylate Photopolymer for Holographic Recording

Phenanthraquinone-doped polymethyl methacrylate (PQ/PMMA) photopolymers are considered to be the most promising holographic storage media due to their unique properties, such as high stability, a simple preparation process, low price, and volumetric shrinkage. This paper reviews the development process of PQ/PMMA photopolymers from inception to the present, summarizes the process, and looks at the development potential of PQ/PMMA in practical applications.

Highly Sensitive Photopolymer for Holographic Data Storage Containing Methacryl Polyhedral Oligomeric Silsesquioxane

Herein, via introducing eight methacryl polyhedral oligomeric silsesquioxane (Ma-POSS), we dramatically enhance the holographic performance of phenanthraquinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymer with excellent characteristics of high sensitivity, high diffraction efficiency, and neglectable volume shrinkage for holographic data storage, the photosensitivity, diffraction efficiency, and volume shrinkage reaching 1.47 cm/J, ∼75%, and ∼0.09%, respectively. Ma-POSS here dramatically enhances the photosensitivity ∼5.5 times, diffraction efficiency more than 50%, and suppressed the volume shrinkage over 4 times. Further analysis reveals that Ma-POSS obviously increased the molecular weight by grafting PMMA to be a star-shaped macromolecule. And the residual C═C of POSS-PMMA dramatically increased the photosensitivity. Moreover, the star-shaped POSS-PMMA acting as a plasticizer dramatically enhances the mechanical properties and so reduces the photoinduced volume shrinkage of PQ/PMMA. Finally, by the use of the POSS-PMMA/PQ in a collinear holography system, it appeared to be promising for a fast but low bit error rate in holographic information storage. The current study thence has not only successfully synthesized photopolymer materials with potential for highly sensitive holographic storage applications but also investigated the microphysical mechanism of the impact of Ma-POSS on the holographic properties of PQ/PMMA photopolymer and clarified the thermal- and photoreaction processes of the POSS-PMMA/PQ photopolymer.

Reconstruction characters of conventional holography using polarization-sensitive material

Polarization holography, recording the amplitude, phase, and polarization of signal wave, may be regarded as the superposition of conventional holography and orthogonal holography. The former implies the signal and reference waves have the identical polarization state in the recording stage, while the latter means that they have the orthogonal polarization state. It is a common sense that in conventional holography, the polarization state of a reconstructed wave is always identical to that of the reading wave. However, predicted by the tensor polarization holography theory, which has been confirmed by many experiments, the polarization state of a reconstructed wave may be different from that of a reading wave. Hence, a question that may arise is which one is correct and why. In this work, we derive the electrical field of a reconstructed wave generated from the hologram that was recorded by the identical elliptically polarized wave at a large angle. The theoretical result shows that there are three kinds of reconstruction characters, and they are confirmed by the designed experiments well. Through the analysis, we find the key to observing that the recording material should be polarization-sensitive; recorded by a nonpolarization sensitive material, the polarization state of the reconstructed wave is always identical to that of the reading wave. The work not only verifies the tensor polarization holography theory, it also enlarges our understanding about conventional holography.

Exposure response coefficient of polarization-sensitive media using tensor theory of polarization holography

We report a method for measuring the exposure response coefficient of polarization-sensitive media using the tensor theory of polarization holography. According to the theory of polarization holography based on the tensor method, the exposure response coefficient of polarization-sensitive media is not only determined by the materials but also affected by the exposure energy. The exposure response coefficient changing with the exposure energy is the key factor in polarization holography for controlling the polarization state of the reconstructed wave. We summarize the change of the polarization state of the reconstructed wave with the exposure energy under different recording conditions and obtain the initial value (about 8.4) of the exposure response coefficient of the polarization-sensitive media. Finally, the null reconstruction of linear polarization wave is realized by using this initial value.