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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. [ABSTRACT FROM AUTHOR]

In the era of big data, the demand for high-density and large-capacity storage technology is increasing day by day. Unlike traditional storage technologies that record data bit by bit, holographic storage uses two-dimensional data pages as the link for reading and writing, adopting a three-dimensional volume storage mode. With advantages such as high storage density, fast data conversion rate, energy efficiency, safety, and ultra-long-term preservation, holographic storage is expected to become the strong competitor for mass cold data storage. This paper focuses on phase-modulated collinear holographic storage and analyzes the current research status of error correction codes for holographic storage. A detailed introduction is provided to an reference beam-assisted low-density parity check (LDPC) code scheme. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Data Acquisition & Processing / Shu Ju Cai Ji Yu Chu Li is the property of Editorial Department of Journal of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We report here bent shape calamitic thermotropic liquid crystal derivatives of 4-amino acetophenone. Compounds were designed having both chalcone and Schiff base as central linkages with various terminal alkoxy chains. All the compounds were synthesized and well characterized. Compounds were screened for their mesomorphic properties using polarizing optical microscope under heating and cooling cycles. Thermograms of all the compounds were studied using differential scanning calorimetry to get phase transition temperatures and enthalpy. Compounds with chain length of eight to twelve carbons showed nematic mesophase. Compounds with higher chain length showed smectic A mesophase under both heating and cooling cycles. [ABSTRACT FROM AUTHOR]

Abstract Zr, Ru and Fe co-doped LiNbO 3 crystals with various level of Zr4+ doping were grown in air by the conventional Czochralski method via the optimum growth condition. The defect structure of Zr:Ru:Fe:LiNbO 3 crystals was analyzed by UV-visible absorption spectra. The holographic storage properties of Zr:Ru:Fe:LiNbO 3 crystals were investigated by two-wave coupling experiment. The results showed that holographic storage performance improved with increase of Zr4+ doping concentration and the Zr (5 mol%):Ru:Fe:LiNbO 3 crystal is promising candidate for holographic storage. Highlights • The Ru:Fe:LiNbO 3 crystal doped with different concentration of ZrO 2 were first grown by Czochralski method. • The absorption edges of Ru:Fe:LiNbO 3 crystal shift to violet direction because of the incorporation of Zr4+ ion. • The absorption edges of Zr:Ru:Fe:LiNbO 3 crystals shift to red with the increase of Zr4+ ion. • The Zr (5 mol%):Ru:Fe:LiNbO 3 crystal has wide dynamic range 19.97, high sensitivity 0.21 and a short response time. [ABSTRACT FROM AUTHOR]

A series of photopolymers based on ethylene glycol phenyl ethyl arylate (EGPEA) monomers and poly(methyl methacrylate) (PMMA) matrix with varying initiator concentrations and sample thicknesses have been synthesized and their optical performance characterized in this study. The advantages of lowering the initiator concentration, including a rather short initiation time within a few seconds; a sharp rising optical response; and a stable saturated diffraction efficiency are demonstrated. The variation in the diffraction efficiency and response time with the exposure energy under various sample thickness and initiator concentrations is examined; a diffraction efficiency as high as 80% and a relatively short response time of 12–39 s are attainable. The dependence of the normalized optical parameter “sensitivity” on the exposure time is depicted, and the peak value of S ranges vastly from about 0.2 to 1.2 × 104 cm/J within a period of 15 s or so, with a maximum value of nearly 1.2 × 104. Favorable evidence of low initiator concentration can further be found when the dependence of the saturated diffraction efficiency with the exposure energy is examined. The data from this study using a low initiator concentration cover a range of exposure energy from 100 to 800 mJ/cm2 and a saturated diffraction efficiency from about 15% to 80%. The successful image reconstruction of 6-membered-ring metal nuts on a hologram based on this EGPEA/PMMA photopolymer system using a reflective holographic recording setup is demonstrated to verify its applicability to holographic storage.

Silicon-based solid state plasma antennas were characterized by its wide radiation range, good stealth characteristic, and dynamic reconfigurability, which have broad application prospects in the future. In this paper, investigations of surface PiN diodes developed for silicon-based reconfigurable holographic antennas have been demonstrated for using millimeter-wave communication systems. The SPiN diodes have been extensively discussed, and the obtained results (simulations and experiments) confirm the applicability of these devices for dynamically reconfigurable antennas. A carrier concentration of 10 18 –10 19  cm −3 has been achieved within the optimized SPiN diode. Reconfigurable holographic antennas based on SPiN diodes that were activated by the injection of dc current were demonstrated in this paper. The resonance frequencies at 60 GHz and 64.5 GHz have been easily achieved by turning on or off different sections of the reconfigurable dipole antenna, while the radiation efficiencies were 85.1% and 83.8%, respectively. A double-layer holographic structure was also investigated in this paper. The study reveals that a novel reconfigurable antenna with SPiN diodes has been formed in a single system and has numerous advantages over the traditional antenna. [ABSTRACT FROM AUTHOR]

A series of Hf: Ru: Fe: LiNbO 3 crystals with various Li composition in the melt were grown by the conventional Czochralski method via the optimum growth condition in the air. The intrinsic defect concentrations and structures of lithium niobate crystals were investigated by using XRD technique and the holographic storage properties were investigated by means of two-wavelength nonvolatile experiments. The results indicate that the concentration of intrinsic defects decreases with the increasing of Li/Nb ratio and the holographic storage properties is obviously improved. The Hf: Ru: Fe: LiNbO 3 crystal with Li/Nb ratio 1.38 has the best holographic storage properties. The experiment results indicated that Hf: Ru: Fe: LiNbO 3 crystal was an outstanding medium for holographic storage applications. [ABSTRACT FROM AUTHOR]

Copyright of Imaging Science & Photochemistry is the property of Imaging Science & Photochemistry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Compared to lead lanthanum zirconate titanate (PLZT), potassium-sodium niobate shows good advances because of its excellent photoelectric response frequency and holographic storage. However, its low transmittance limits its application in photoelectrical controllers. To address this issue, lanthanum was introduced as a dopant, and the properties of the resulting ceramics were evaluated using both experimental and theoretical approaches. The (1-x)(K 0.5 Na 0.5 )NbO 3 -xLa 2 O 3 (KNN-xL; x = 0.005, 0.010, 0.015, 0.020) transmittance ceramics were prepared by traditional low-pressure sintering process. Among the ceramics examined, KNN-0.015L achieved the widest band gap (Eg) of 3.108 eV and the highest transparency of 74%; both values are higher than those of PLZT (band gap = 3.10 eV, transparency = 70%) prepared by hot-press sintering. The transition rule was evaluated by density functional theory (DFT) to validate the experimental results obtained. Additionally, the related mechanism of transparency variation induced by electronic structure and grain size modulation was discussed thoroughly. [ABSTRACT FROM AUTHOR]

Holographic recording media can store the amplitude and the phase, or the complex amplitude, of a beam on the basis of holography. Owing to this characteristic, digital data can be encoded onto the complex amplitude of a signal beam in holographic data storage. However, most of conventional holographic storage systems encode digital data onto the amplitude alone because there are difficulties for modulating and detecting the phase. To solve the difficulties, a holographic storage system using digital holographic techniques has been proposed. With the help of digital holographic techniques, it is possible to modulate and detect the complex amplitude of a signal beam. Moreover, the proposed system can modulate the complex amplitude of a reference beam. In this paper, by making use of the capability, a correlation-based multiplexing with uncorrelated reference beams is demonstrated in the proposed system. Multiple holograms can be recorded in the same volume of a recording medium with no need for mechanical movements. Experimental results show that the proposed system with a correlation-based multiplexing can improve the storage capacity and can utilize the full potential of a recording medium without crosstalk noise stem from the optical setup. [ABSTRACT FROM AUTHOR]

Holographic data storage system is a candidate for the information recording due to its large storage capacity and high transfer rate. We propose an unequally spaced four levels phase encoding in the holographic data storage system here. Compared with two levels or three levels phase encoding, four levels phase encoding effectively improves the code rate. While more phase levels can further improve code rate, it also puts higher demand for the camera to differentiate the resulting smaller grayscale difference. Unequally spaced quaternary level phases eliminates the ambiguity of pixels with same phase difference relative to reference light compared to equally spaced quaternary levels. Corresponding encoding pattern design with phase pairs as the data element and decoding method were developed. Our encoding improves the code rate up to 0.875, which is 1.75 times of the conventional amplitude method with an error rate of 0.13 % according to our simulation results. [ABSTRACT FROM AUTHOR]

Holographic performances are investigated experimentally in polyvinyl alcohol/acrylamide photopolymer (PVA/AA) films with thickness of 200 μm. Acrylamide (AA) and acrylic acid (AAc) are both used as monomers. It is demonstrated that the performances are improved due to addition of AAc monomer. The improved photopolymer shows higher diffraction efficiency and exposure sensitivity. The maximal diffraction efficiency is about 52%. At the same time, the photopolymer presents low scattering noise due to addition of AAc. The angular selectivity bandwidth of the optimum photopolymer is also measured. [ABSTRACT FROM AUTHOR]

Volume holographic storage has be paid much attention as the increasing requirement of data storage. To overcome the disadvantage of storage medium properties and low popularity of holographic storage, the demonstration instrument of volume holographic storage with polymeric holographic disc is investigated. The preparation of polymeric disc is thermal initiation of radical polymerization. In the materials, poly methyl methacrylate is matrix, and phenanthrenequinone is photosensitizer. The holographic disc with high thickness and transparency has the ability of write once and read permanent, and its thermal and optical stability is excellent. The disc is suitable to enhance the storage capacity and reduce the cost of device because its sensitive wavelength covers the wavelength of DPSS laser.There are high diffraction efficiency and image quality by measuring the device properties. The multiplexing method will be able to achieve high storage density on one spot. The new demonstration instrument can demonstrate all of the process including data collection, process, storage and read. The preparation of medium, molding technics, and photochemical mechanism of the photopolymer can present to the student for understanding next information storage technology. [ABSTRACT FROM AUTHOR]

Organic materials containing carbazole moiety are promising photonic materials for numerous applications including holographic storage, real-time optical processing, imaging, non-destructive testing and phase conjugation. The purpose of our research is the synthesis of functionalised polymers and copolymers of carbazole based derivatives containing p-nitrophenyl diazene moiety and study their optical response in thin film matrices. Some qualitative results concerning their potential in photorefractivity are reported. [ABSTRACT FROM AUTHOR]

Holographic data storage is a promising technology that provides very large data storage capacity, and the multiplexing method plays a significant role in increasing this capacity. Various multiplexing methods have been previously researched. In the present study, we propose a shift-peristrophic multiplexing technique that uses spherical reference waves, and experimentally verify that this method efficiently increases the data capacity. In the proposed method, a series of holograms is recorded with shift multiplexing, in which the recording material is rotated with its axis perpendicular to the material's surface. By iterating this procedure, multiplicity is shown to improve. This method achieves more than 1 Tbits/inch² data density recording. Furthermore, a capacity increase of several TB per disk is expected by maximizing the recording medium performance. [ABSTRACT FROM AUTHOR]

In this study, we proposed a method to determine the optimal focal position for micro-holographic storage systems, using vector diffraction theory; the theory provides exact solutions when the numerical aperture (NA) exceeds 0.6. The best diffraction focus was determined by the position and wavelength corresponding to minimal spherical aberration. The calculated refractive index modulation, polarization illumination, and boundary conditions at the interface of different media were analyzed. From the results of our analysis, we could confirm the size of micrograting as a function of NA and wavelength, based on vector diffraction theory, compared with scalar diffraction theory which defines the micrograting by λ/(2NA). To demonstrate our analysis, we adapted an optical alignment method using a Twyman-Green interferometer, and could obtain good agreement between analysis and experimental results. [ABSTRACT FROM AUTHOR]

Big data creates numerous exciting possibilities for organizations, but first they must figure out where they're going to store all that information. [ABSTRACT FROM PUBLISHER]

The exposure schedule model for uniform diffraction efficiency is extended to be suitable for the partially overlapping multiplexing method. The proposed model is based on solving an optimization problem. Fifty holograms were multiplexed using the exposure schedule calculated with the extended model. The material used in the experiment is based on the photopolymerization of a free radical. By comparing the intensity of the reconstructed images during recording with that readout after recording, the calculated exposure schedule is verified to be effective to realize the uniform diffraction efficiency for the multiplexing holographic storage. [ABSTRACT FROM AUTHOR]

It has been suggested to use LiNbO3:Fe, Mn crystal for solving the problem of information volatility during the read-out process with all-optical facilities, but the minute order response time is far from the requirements for the real-time information processing. We present the nonvolatile holographic storage properties of LiNbO3:Hf, Fe, Mn. The response time is shortened to 5.0 s, and the sensitivity S' is enhanced to 0.22 cm/J in this triply doped crystal. The experimental results show that the HfO2 doping threshold is 5.0 mol.%. Thus it seems that we have found a useful tetravalent dopant for LiNbO3:Fe, Mn that can obviously improve the nonvolatile holographic recording sensitivity. [ABSTRACT FROM AUTHOR]

Photopolymers are very interesting as optically sensitive recording media due to the fact that they are inexpensive, self-processing materials with the ability to capture low-loss, high-fidelity volume recordings of 3D illuminating patterns. We have prepared this paper in part in order to enable the recognition of outstanding issues, which limit in particular the data storage capacity in holographic data storagemedia. In an attempt to further develop the data storage capacity and quality of the information stored, that is, the material sensitivity and resolution, a deeper understanding of such materials in order to improve them has become ever more crucial. In this paper a brief review of the optimisation of photopolymer materials for holographic data storage (HDS) applications is described. The key contributions of each work examined and many of the suggestions made for the improvement of the different photopolymer material discussed are presented. [ABSTRACT FROM AUTHOR]

Holographic polymer-dispersed liquid crystals are promising materials for switchable holograms, optical data storage, tunable beam deflectors and various diffractive optical elements, which can be addressed by electric fields. The present paper describes investigations on the grating formation in a model system. The results of holographic and calorimetric experiments are in good agreement with a reaction-diffusion model. [ABSTRACT FROM AUTHOR]

A novel Fuchsin Basic-sensitised photopolymer was prepared and studied as a holographic recording material using He-Cd and Nd:YAG lasers. The results indicate that the material shows attractive recording characteristics, which include diffraction efficiency, sensitivity, refractive index modulation, volume shrinkage, etc. Various photochemistry parameters were obtained by using Levenberg-Marquardt's algorithms to fit the photobleaching model. The storage life of photopolymer film was studied, and holograms were successfully recorded and reconstructed in high fidelity and contrast. [ABSTRACT FROM AUTHOR]

Abstract: The holographic characteristics in phenanthrenequinone and Zinc methylacrylate doped poly-(methyl methacrylate) photopolymers are experimentally studied. The role of ZnMA molecules which is to accelerate the photochemical reaction in material is confirmed by experiment. The doping of ZnMA component results in a higher diffraction efficiency and photosensitivity than typical phenanthrenequinone doped poly-(methyl methacrylate) system. Moreover, the response region and dynamic range are obviously improved. [Copyright &y& Elsevier]

Abstract: We report experimental observation of ultra-long lifetime UV-induced absorption in undoped and 5mol.% Mg-doped congruent lithium niobate crystals between 400nm and 2500nm wavelength range. The saturated absorption coefficient change in undoped congruent lithium niobate was about 3 to 7 times that in Mg-doped congruent lithium niobate in the mid-infrared spectrum. The UV-illuminated LiNbO3:Mg was fully recovered in the dark after 2 days, whereas the undoped congruent LiNbO3 still exhibited nontrivial infrared absorption. We attribute the cause of the UV-induced absorption to the creation of hole-trapped intermediate states O− near lithium vacancies. [Copyright &y& Elsevier]

Abstract: The dark enhancements with various exposure energies are studied in thick PQ/PMMA photopolymer. Considered the weak molecules diffusion of PQ component and the grating detuning, a new mechanism of dark reaction is proposed to explain the dark enhancement. Moreover, the influences of dark reaction on Bragg angular selectivity and grating recording are analyzed. The results are beneficial to the practical holography application. [Copyright &y& Elsevier]

Retrieving original user data from holographic data storage systems is mainly affected by two‐dimensional (2D) intersymbol interference; the minimisation of this interference not only improves the system performance, but it also increases the storage density for page‐oriented storage systems. An iterative detection that is supported by the readback signal is proposed. The decoded symbols are passed through a 2D partial response target before they are combined with the output of the equaliser, leading to the generation of a refined information source that improves the channel‐detection performance. The simulation results show that the proposed structure provides a gain of ∼1–2 dB; furthermore, the combinative quality of the proposed model and a page‐based search scheme were analysed as well. [ABSTRACT FROM AUTHOR]

Holographic data storage (HDS) provides the high storage density and fast data‐access rate because of the page‐oriented data processing, and by the same reason, the performance of retrieving original user data is mainly affected by 2D intersymbol interference (ISI). An 8/10 2D modulation code for mitigating a 2D ISI in HDS systems is proposed. The simulation results show that the proposed code provides a gain of approximately 6 dB at BER of 10−6 compared to the raw signal without encoding. Especially, in comparison to a recently suggested 6/8 modulation code, the proposed scheme not only offers a higher code rate, but it also exposes a boost of the system performance under misalignment conditions. [ABSTRACT FROM AUTHOR]

Abstract: Holographic diffraction gratings have been induced at room temperature (RT) using red light (633nm), in a liquid crystalline side chain cyano-azobenzene polymethacrylate polymer. Stable gratings have been obtained under simultaneous irradiation with the interference pattern created with two coherent linearly polarized red light beams and UV (around 350nm) unpolarized light. The main contributions to the diffraction efficiency can come from the photoinduced orientation of the azo units and perhaps from changes in the light transmitted through the regions of the film that have been illuminated with both red and UV light and those only illuminated with the UV light. Higher efficiency is achieved if the red light polarization is perpendicular to the grating vector than if it is parallel to that vector. Stable gratings have also been induced with either sequential or simultaneous irradiation with blue (488nm) linearly polarized light and the red interference pattern. The contributions to the efficiency can have the same origin as under UV and red light illumination. The highest efficiency is achieved under simultaneous illumination with both blue and red light polarizations perpendicular to the grating vector. [Copyright &y& Elsevier]

Abstract: We present the efficiency of holographic recording in a series of conjugated polymers of the polyphenylenevinylene type and correlate the results with the molecular structure. Diffraction gratings were recorded at three different wavelengths in order to distinguish between the effects of absorbance and molecular structure. It is found that polymer films with pure alkyl chains do not give rise to high diffraction efficiency. Thick films of most of the materials were found to yield a diffraction efficiency on the order of 5%, with MEH-PPV film gives a diffraction efficiency exceeding 25%. Atomic force microscope scans of the gratings show that a surface relief grating is also produced. The gratings were found to be stable for more than one year, when they are kept in the dark. [Copyright &y& Elsevier]