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Proceedings Paper

Investigation of the temporal response and volume changes occurring during grating formation in photopolymer
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Paper Abstract

In this paper we analyze the evolution of the refractive index modulation when recording gratings in an acrylamide based photopolymer. A nonlocal diffusion model is used to predict theoretically the grating evolution. The model has been developed to account for both nonlocal spatial and temporal effects in the medium which can be attributed to polymer chain growth. Previously it was assumed that the temporal effect of chain growth could be neglected. However temporal effects both due to chain growth and monomer diffusion are shown to be significant, particularly of short recording periods. The diffusion model is solved using a Finite-Difference Time-Domain technique to predict the evolution of the monomer and polymer concentrations throughout grating recording. Using independently measured refractive index values for each component of the recording medium, the Lorentz-Lorenz relation is used to determine the corresponding refractive index modulation. Gratings recorded for short exposure times with the diffraction efficiency growth monitored in real time both during and after recording are presented. The effect of volume shrinkage of polymer on grating evolution is also examined. The temporal response of the material and monomer diffusion is shown to influence refractive index modulation post-exposure. The inclusion of the nonlocal temporal response and the use of the Lorentz-Lorenz relation are shown to be necessary to accurately describe this polymerization process.

Paper Details

Date Published: 1 September 2005
PDF: 10 pages
Proc. SPIE 5939, Organic Holographic Materials and Applications III, 59390J (1 September 2005); doi: 10.1117/12.617272
Show Author Affiliations
John V. Kelly, Univ. College Dublin (Ireland)
Michael R. Gleeson, Univ. College Dublin (Ireland)
Ciara E. Close, Univ. College Dublin (Ireland)
Feidhlim T. O'Neill, Univ. College Dublin (Ireland)
John T. Sheridan, Univ. College Dublin (Ireland)

Published in SPIE Proceedings Vol. 5939:
Organic Holographic Materials and Applications III
Klaus Meerholz, Editor(s)

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