The differaction efficiency,sensitivity and storage life of Methylene Blue sencitized poly (vinyl chloride) film was improved by the addition of an electron donor in the matrix. The
addition of pyridine enhanced the diffraction efficiency by two times and storage life of the
gratings was increased to 2-3 days.
Sudha Kartha,C(Optical society of America, June 20, 2004)
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Abstract:
A methylene-blue-sensitized polymer blend of polyvinyl alcohol and polyacrylic acid is fabricated and
tested for holographic recording. It was found to have good characteristics such as high sensitivity,
storage stability, ease of fabrication, and environmental stability. Optimization of the ratio of polyvinyl
alcohol polyacrylic acid, the sensitizer concentration, pH, energy, diffraction efficiency measurements,
etc., have been done. pH is found to have a great influence on the recovery of the dye in this matrix.
The results of experimental investigations into the properties of this new material are reported.
Sudha Kartha,C(Taylor and francis, October 20, 2003)
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Abstract:
Polymer materials find application in optical storage technology,
namely in the development of high information density and fast access type
memories. A new polymer blend of methylene blue sensitized polyvinyl alcohol
(PVA) and polyacrylic acid (PAA) in methanol is prepared and characterized
and its comparison with methylene blue sensitized PVA in methanol and
complexed methylene blue sensitized polyvinyl chloride (CMBPVC) is presented.
The optical absorption spectra of the thin films of these polymers
showed a strong and broad absorption region at 670-650 nm, matching the
wavelength of the laser used. A very slow recovery of the dye on irradiation was
observed when a 7:3 blend of polyvinyl alcohol/polyacrylic acid at a pHof 3.8
and a sensitizer concentration of 4.67 10 5 g/ml were used. A diffraction
efficiency of up to 20% was observed for the MBPVA/alcohol system and an
energetic sensitivity of 2000 mJ/cm2 was obtained in the photosensitive films
with a spatial frequency of 588 lines/mm.
Sudha Kartha,C(Indian academy of science, 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.
Sudha Kartha,C(American Institute of Physics., January 13, 2007)
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Abstract:
Poly(methyl)methacrylate was made photoconducting by molecular doping and the
photoconductivity was investigated using modulated photocurrent technique . Low-temperature
current-voltage measurements showed that the transport mechanism was thermally activated
hopping. An experimental investigation of the photoconductivity action spectrum along with
theoretical calculation enabled an estimation of the diffusion coefficient of the material. The
presence of states with a distribution of lifetimes could be understood from the frequency response
of the photocurrent . The photocurrent was due to the field-assisted dissociation of these states.
Sudha Kartha,C(Taylor and francis, March 13, 2005)
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Abstract:
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 efficiency of 6.3% was obtained without any fixing at a dye
concentration of 9.3 10 4 mol/l at an exposure of 750 mJ/cm2. The material is
attractive on account of its reusability.
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.