Rani, Joseph(Department of Polymer Science and Rubber Technology, November 8, 2006)
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Abstract:
Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the
storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride
concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the
optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or
thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.
Beena,Mary John; Sudha Kartha, C(Department of Physics, January , 2008)
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Abstract:
Holographic technology is at the dawn of quick evolution in various new
areas including holographic data storage, holographic optical elements, artificial
intelligence, optical interconnects, optical correlators, commerce, medical practice,
holographic weapon sight, night vision goggles and games etc. One of the major
obstacles for the success of holographic technology to a large extent is the lack of
suitable recording medium.
Compared with other holographic materials such as dichromated gelatin
and silver halide emulsions, photopolymers have the great advantage of recording
and reading holograms in real time and the spectral sensitivity could be easily
shifted to the type of recording laser used by simply changing the sensitizing dye.
Also these materials possess characteristics such as good light sensitivity, real
time image development, large dynamic range, good optical properties, format
flexibility, and low cost. This thesis describes the attempts made to fabricate
highly economic photopolymer films for various holographic applications.
In the present work, Poly (vinyl alcohol) (PVA) and poly (vinyl chloride)
(PVC) are selected as the host polymer matrices and methylene blue (MB) is used
as the photosensitizing dye. The films were fabricated using gravity settling
method. No chemical treatment or pre/post exposures were applied to the films.
As the outcome of the work, photopolymer films with more than 70% efficiency, a
permanent recording material which required no fixing process, a reusable
recording material etc. were fabricated.
Rani, Joseph(Indian Academy of Sciences, February 24, 2003)
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Abstract:
Significant results of our experimental investigations on the dependence of pH on real time
transmission characteristics on recording media fabricated by doping PVC with complexed methylene blue
are presented. The optimum pH value for faster bleaching was found to be 4 . 5. In typical applications, the
illumination from one side, normal to the surface of this material, initiates a chemical sequence that records
the incident light pattern in the polymer. Thus direct imaging can be successfully done on this sample. The
recorded letters were very legible with good contrast and no scattering centres. Diffraction efficiency
measurements were also carried out on this material.
A new photopolymerizable recording media is introduced based on poly
(vinyl alcohol) and vinyl acetate sensitized with methylene blue. It is observed
that this MBPVA/VAc system can be reused a number of times without
significant decrease in diffraction efficiency. The PVA-VAc ratio was optimized
at 2:1. Diffraction efcienc4y of 6.3% was obtained without any fixing at a dye
concentration of 9.3 x 10- mol/l at an exposure of 750mJ/cm2. The material is
attractive on account of its reusability.