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

Abstract

Multiple grating phenomena have been observed in a number of photorefractive systems"2, and interaction between such gratings has been proposed as the basis for the demonstration of interesting optical effects such as velocity filtering3 and image differentiation4. We are investigating grating interactions in azo-dye doped photorefractive polymers with a view to assessing their suitability for use in such information processing applications. We report the results of wave-mixing investigations on two photorefractive polymer systems. The first system is a conventional guest-host photorefractive polymer based on the photoconducting host PVK:ECZ:TNF and the nonlinear chromophore trans-4-N,N-diethylamino-(E)-cinnamonitrile (DEACST). The results of degenerate four wave mixing (DFWM) and two beam coupling (TBC) experiments in this composite are described well by the orientational enhancement model5. The second system is a hybrid composite consisting of PVK:DEACST:ECZ:TNF and the well known azo-dye disperse red 1 .In this system, gratings may be written via the photochemical mechanism of photoisomerization as well as the photorefractive effect. We suggest that the diffraction behaviour of the hybrid composite involves a disruption of the light-induced azo-dye molecular orientation by the space charge field.