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Freiburger Materialforschungszentrum
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You are here: Home Events Prof. Andrey Veniaminov "Relaxation of Photinduced Gratings for Material Studies and Hologram Formation"

Prof. Andrey Veniaminov "Relaxation of Photinduced Gratings for Material Studies and Hologram Formation"

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Centre "Information Optical Technologies" and Department of Photonics and Optical Informatics, National Research University of IT, Mechanics and Optics, St.Petersburg, Russian Federation

What
  • Seminar
When Jun 05, 2013
from 02:15 PM to 03:00 PM
Where Hörsaal Makromolekulare Chemie, Stefan-Meier-Str. 31, Freiburg
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The primary aim of holography is transformation of wavefronts that results in optical elements with otherwise inaccessible properties, extra-dense information storage, 3D images, and other applications. Somewhat extraordinary is use of holograms written in bulk materials to study those materials: monitoring the properties of holograms gives an access to valuable information about molecular transformations, microscopic mobility and other phenomena that make them change. The approach known as holographic grating relaxation, or forced Rayleigh scattering, or transient grating technique, is especially suitable, due to microscopic spatial period, for extremely slow diffusion, such as that characteristic of polymer glasses. 

Doping material with quinone species capable of forming chemical bonds with sur-rounding matter under exposure has made it possible to study diffusion of small molecular probe in glassy polymers and even much slower motions of photolabelled macromolecules. In spatially heterogeneous materials such as latex films, diffusion coefficients and mean dis-placements of a molecular tracer in different microdomains were measured by means of the holographic technique, even if the materials look transparent and their heterogeneity does not manifest itself in light scattering.

The peculiar nonmonotonous relaxation of photoinduced gratings originating from competing diffusion of dye molecules and macromolecules has become a technique for self-development of efficient and stable volume holograms recorded in quinone-doped polymer glass. These holograms serve as reliable optical elements with subnanometer spectral selectiv-ity, such as notch-filters, multiplexers, etc. 
 

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