Abstract-Holographic data storage is a new optical technology which allows an important number of bits to be stored in a recording material. In this work, holographic data pages were stored in a PVA/acrylamide photopolymer layer using a peristrophic multiplexing method. This material is formed of acrylamide photopolymers, which are considered interesting materials for recording holographic memories. Moreover, a hybrid ternary modulation (HTM) was used to reduce the zero frequency of the Fourier Transform (FT) of the object. A liquid crystal device (LCD) was optimized to modify the object beam in order to obtain data pages with the HTM.Index Terms-Liquid-crystal devices, multiplex holography, optical storage and recording materials.
The harmonic balance method is used to construct approximate frequency-amplitude relations and periodic solutions to an oscillating charge in the electric field of a ring. By combining linearization of the governing equation with the harmonic balance method, we construct analytical approximations to the oscillation frequencies and periodic solutions for the oscillator. To solve the nonlinear differential equation, firstly we make a change of variable and secondly the differential equation is rewritten in a form that does not contain the squareroot expression. The approximate frequencies obtained are valid for the complete range of oscillation amplitudes and excellent agreement of the approximate frequencies and periodic solutions with the exact ones are demonstrated and discussed.
This paper presents the results obtained when holographic gratings were stored with a spatial frequency of 954 and 2663 lines∕mm in transmission geometry and 4600 lines∕mm in reflection geometry in a polyvinyl alcohol/acrylamide-based material. Photopolymers are materials that give good results at low frequencies, but their diffraction efficiency (DE) decreases at high frequencies. A chain transfer agent, 4,4 ′ -azobis (4-cyanopentanoic acid) (ACPA) was incorporated in the material composition to improve spatial resolution. Furthermore, a curing process was applied to the stored gratings in order to maintain the DE stable over time. The DE and shrinkage for symmetric holographic transmission and reflection gratings were measured to evaluate their quality and quantify the improvement produced by ACPA.
High-spatial-frequency fringes associated with reflection holographic optical elements are difficult to obtain with currently available recording materials. In this work, holographic reflection gratings were stored in a polyvinyl alcohol/acrylamide photopolymer. This material is formed of acrylamide photopolymer, which is considered interesting material for optical storage applications such as holographic memories. The experimental procedure for examining the high-spatial-frequency response of this material is explained, and the experimental results obtained are presented. With the aim of obtaining the best results, the performance of different material compositions is compared.
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