<title>Multiple grating formation in photorefractive polymers with azo-dye chromophores</title>

Abstract

Photorefractive polymers which incorporate azo-dyes as the non-linear chromophore element, can be used not only for generating gratings by the photorefractive effect, but also by photoisomerization of the azo-dye. In the latter mechanism, repeated trans-cis isomerization causes the chromophore molecules to become aligned at right angles to the laser polarization direction, thereby making the material birefringent.These two phenomena are to a large degree independent, and can be studied separately, by appropriate choice of polarization direction of the interacting beams. Furthermore, the diffraction efficiency of the photorefractive gratings is a very sensitive function of the poling field strength, while that of the photoisomerization gratings is less so.In this work, we investigate the components diffracted from each of these gratings formed in a hybrid photorefractive polymer material PVK:TNF:DEACST:disperse red 1. We then explore the possibility of performing some simple optical processing applications, exploiting the flexibility provided by this multiple grating process. A scheme for producing a novelty filter, which displays only the moving parts of a scene is considered.The limitations of these films for such processing applications are discussed.

<title>Grating competition effects in photorefractive polymers</title>

“…lT PI +lpR -2cosijpR (7) The best fits to the DFWM data according to this model are shown for the SSS and SSP arrangements in Figure 6 as solid lines. The photorefractive parameters (A, C/A and Es) were obtained from the SSP data by considering the points in the high field region, where the photorefractive effect dominates, giving A =-1.79 x l019 m2V2, C/A = -2.67 and E5 93 Vim' .…”