Proceedings of Topical Meeting on Optoinformatics (pdf-format, 1.21 ...

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.