Characterization of the DuPont photopolymer for three-dimensional holographic storage (original) (raw)
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Applied Optics, 2003
Poly͑vinyl alcohol-acrylamide͒ photopolymers are materials of interest in the field of digital information storage ͑holographic memories͒. We analyzed the behavior of a 1-mm-thick photopolymer. Using a standard holographic setup, we recorded unslanted diffraction gratings. The material has high angular selectivity ͑0.4°͒, good sensitivity ͑88 mJ͞cm 2 ͒, and small losses caused by absorption and scattering of light. It also has a high maximum diffraction efficiency ͑70%͒. A significant induction period was seen in the material. The authors hypothesize that, during most of this induction period, polymerization does in fact take place but is not reflected in the appearance of the diffracted light until a certain threshold value of exposure is reached.
3 Dimensional analysis of holographic photopolymers based memories
Optics Express, 2005
One of the most interesting applications of photopolymers is as holographic recording materials for holographic memories. One of the basic requirements for this application is that the recording material thickness must be 500 µm or thicker. In recent years many 2-dimensional models have been proposed for the analysis of photopolymers. Good agreement between theoretical simulations and experimental results has been obtained for layers thinner than 200 µm. The attenuation of the light inside the material by Beer's law results in an attenuation of the index profile inside the material and in some cases the effective optical thickness of the material is lower than the physical thickness. This is an important and fundamental limitation in achieving high capacity holographic memories using photopolymers and cannot be analyzed using 2-D diffusion models. In this paper a model is proposed to describe the behavior of the photopolymers in 3-D. This model is applied to simulate the formation of profiles in depth for different photopolymer viscosities and different intensity attenuations inside the material.
Holographic Memory Photopolymer Materials
2007
Data flow and its storage is one of the immediate requirements in present information age. There is a huge demand for a suitable storage media for immediate use and for data archive. Photopolymers are one of the most interesting materials with great storage potentials at extremely low cost. Photopolymers are attractive optical recording materials for holography, optical image multiplexing, holographic optical devices, and so forth because they have the capabilities of recording holograms of high spatial frequency and exhibit high diffraction efficiency. In this thesis we study and optimize various water soluble photopolymer compositions for their data storage capability as well as a good recording media using optical interferometry. Such optimized compositions are selectively sensitized using red to blue sensitizing dyes for optimum information storage. We also present two newly synthesized dyes absorbing in blue region as a promising media for holographic data storage with high res...
Improvement of photopolymer materials for holographic data storage
Journal of Materials Science, 2009
The one-dimensional diffusion equation, which governs the temporal evolution of holographic grating formation in photopolymers, which includes the non-local material response, the generalized dependence of the rate of polymerization on the absorbed illuminating intensity and the inclusion of our material's response to initiation and inhibition effects has been previously studied and presented. The resulting analytic expressions for the monomer and polymer concentrations have been derived and their validity tested against experimental data using a four-harmonic, numerical fitting regime. In this paper we examine the spatial frequency response of our photopolymer material and using our improved NPDD model we fit experimentally obtained data and extract estimates for material parameters. We attempt to improve our material's spatial frequency response with the addition of chain transfer agents to reduce the polymer chain length formed and the non-local chain-length variance. Achieving this should increase the locality of the polymer chains and hence cause an improvement in the spatial frequency response of the material. It is a material's response to high spatial frequencies, which determines a material's resolution and data storage density.
A Review of the Optimisation of Photopolymer Materials for Holographic Data Storage
Physics Research International, 2012
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 storage media. 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.
2006
The characterization of the behavior of photopolymers is an important fact in order to control the holographic memories based on photopolymers. In recent years many 2-dimensional models have been proposed for the analysis of photopolymers. These models suppose that the photopolymer layer is homogeneous in depth and good agreement between theoretical simulations and experimental results has been obtained for layers thinner than 200 μm. The attenuation of the light inside the material by Beer's law is an important factor when higher thickness are considered. In this work we use a Finite-Difference method to solve the 3 dimensional problem. Now diffusion in depth direction and the attenuation of the light inside the material by Beer's law are also considered, the influence of the diffusivity of material in the attenuation of the refractive index profile in depth is analyzed.
Multiplexing holograms in an acrylamide photopolymer
Proceedings of Spie the International Society For Optical Engineering, 2006
A peristrophic multiplexing method is used to store various diffraction gratings at the same spot in the material. This material is formed of acrylamide photopolymers which are considered interesting materials for recording holographic memories. They have high diffraction efficiency (ratio between diffracted and incident beams), high energetic sensitivity and optical quality, and developing processes are not necessary. In this work, the photopolymer is composed of acrylamide (AA) as the polymerizable monomer, triethanolamine (TEA) as radical generator, N,N'methylene-bis-acrylamide (BMA) as crosslinker, yellowish eosin (YE) as sensitizer and a binder of polyvinyl alcohol (PVA). The layers of material obtained are approximately 1 mm thick. Using holographic recording schedules, the exposure energy each hologram should receive in order to achieve uniform diffraction efficiency is optimized. The purpose of these recording schedules is to enable full advantage to be taken of the whole dynamic range of the material and to share it between the individual holograms. The Scheduled Exposure Method (SEM) and the Incremental Exposure Method (IEM) are the two multiplexing schedules used to determine the recording times. Having determined these times, the results obtained with both methods are compared to ascertain which method enables the greatest number of holograms to be recorded with the highest, most uniform diffraction efficiencies.
Improved maximum uniformity and capacity of multiple holograms recorded in absorbent photopolymers
Optics Express, 2007
In order to use photopolymers in the recording of holographic memories, high physical thickness is required. This generates many problems associated with the attenuation of light in the recording due to Beer's law. One of the more significant disadvantages is the fact that there are differences between the physical thickness of the material and the optical thickness of the holograms recorded. The optical thickness characterizes the angular selectivity of the holograms and determines the separation between two consecutive holograms in angular peristrophic multiplexing. In this work we propose a new method to record many holograms multiplexed with similar diffraction efficiency values taking into account the different effective optical thickness of each hologram.
Recording of multiple holograms in photopolymer films
Applied Optics, 1992
Multiple images were recorded in DuPont HRF-150 photopolymer as transmission holograms by using angle multiplexing. Agreement with Kogelnik's two-wave diffraction theory for phase gratings, the time considerations and its effect on dynamic range, the necessity of a pre-illumination pulse, and good image quality at readout are reported.