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36 OPTOINFORMATICS’05 The technology without above mentioned lack for receiving <strong>of</strong> superposed holograms on the same area <strong>of</strong> sample is proposed. The registration <strong>of</strong> each superposed hologram takes place on the recording area <strong>of</strong> multiplex hologram that possesses homogeneous distribution <strong>of</strong> light-sensitive substrate. There was shown an ability <strong>of</strong> recording from 5 up to 8 holograms with diffraction efficiency more 70% and selectivity contour close to calculated [3] . This method with multibeam record combination allows to multiplex <strong>of</strong> different interference patterns for the purpose <strong>of</strong> periodic and fractal structure design <strong>of</strong> predetermined configuration. Elements on basis <strong>of</strong> above structures with specific properties could be required in different areas <strong>of</strong> science and technology. 1. C. R. Simovski, P. A. Belov. Low-frequency spatial dispersion in wire media, //Phys. Rev. E 70, 046616, 2004. 2. O. V. Andreeva, O. V. Bandyuk, A. A. Paramonov, et al. Transmissive volume holograms in a polymeric medium with phenanthroquinone, //Journal <strong>of</strong> Optical Technology, 67(12), 1043, 2000. 3. Kogelnik H. Coupled Wave Theory for Thick Hologram Gratings, //The Bell System Technical Journal, 48(9), 2909-2947, 1969.
SAINT-PETERSBURG, October 17 – 20, 2005 37 DIGITAL HOLOGRAMS REPLICATIONS WITH POLYVINYL ALCOHOL M.P. Hernández-Garay, A. Olivares-Pérez, I. Fuentes-Tapia, S. Toxqui-López, Instituto Nacional de Astr<strong>of</strong>ísica Óptica y Electrónica, Optic Department, Tonantzintla, 72000, Puebla, México E-mail: mgaray@inaoep.mx, olivares@inaoep.mx Many applications in the industry have the polyvinyl alcohol (PVA). It is known as material for holographic register [1] . We present the analysis <strong>of</strong> the influence <strong>of</strong> some variants in the record process. Obtaining as final result the quantitative results <strong>of</strong> the diffraction efficiency parameter in the replication <strong>of</strong> digital holograms under environmental conditions. Process operates on the principle <strong>of</strong> free radical chain polymerisation; subsequent hydrolysis converts the polyvinyl acetate to polyvinyl alcohol [1] . In partially hydrolysed grades the vinyl alcohol content is such that the entire molecule is freely soluble in water and depends his degree <strong>of</strong> hydrolysis and viscosity is application area. Taking advantage <strong>of</strong> the structure <strong>of</strong> the polymer and controlling his physical and chemical properties, the PVA is used like holographic recording material determining the efficiency <strong>of</strong> the gratings for every composition and procedure [2] . Since the late 1960s, a variety <strong>of</strong> photopolymer materials have been used to fabricate holograms [3] . For our case two indispensable processes exist in the replication <strong>of</strong> the holograms, the heat and the radiation to which the samples surrender. The polymerization is realized by two activation processes, the heat (thermo treated) and radiation (photo treated); every activation process is applied in a different way during the method that we have used doing a control on these. Three types <strong>of</strong> solutions were obtained, with different three PVA's concentration (hydrolysed). The base film was obtained realized first changing the time <strong>of</strong> dried in muffle and thickness for every case as follows: The basic PVA material was dissolved in bi-distilled water heater at 90 o C to obtaining a PVA aqueous solution. With three different PVA concentrations: These three solutions have the following characteristics; you can see the Table 1. We prepared films with an area <strong>of</strong> 2 x 2 cm 2 , on glass substrate <strong>of</strong> 4 x 4 cm 2 . In the first instance the polymerization <strong>of</strong> the films were realized by direct heat in muffle, with a temperature between 70 o C and 80 o C. Table 1. Characteristics at different solutions Liquid solution pH Density (grs/ml) Refraction index 1 7.13 0.914 1.3449 2 7.20 2.16 1.3515 3 7.01 1.447 1.3385 The appearance <strong>of</strong> the record films and their pattern result <strong>of</strong> storage processes under the conditions and characteristics shown in the table 1 appear in the figure 1. Effect <strong>of</strong> the film’s thickness in the process <strong>of</strong> storage is an important parameter to realize the process <strong>of</strong> photopolymerization, determining the sensitivity and the storage capacity. [4] The solutions 2 and 3 it has PVA's major concentration therefore it is difficult and not viable to realize the storage in these solutions. The difficulties in the storage for these solutions were precisely to the thickness <strong>of</strong> the film were much major then solution 1, with a degree <strong>of</strong> hydrolysis minor, impeding the process <strong>of</strong> polymerization.
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