The influence of an incoherent wave on polarization gratings written in a p
hotoanisotropic material is investigated. For the example of a polarization
grating written with two orthogonal circular polarized waves the diffracti
on efficiency was found to change by adding a third incoherent wave. A theo
retical description of the modified grating is given. Using a simple model
the alteration of the diffraction efficiency is estimated and found to be i
n good agreement with the experimental results. (C) 2000 Elsevier Science B
.V. All rights reserved.