Effect of field-dependent photogeneration on holographic contrast in photorefractive polymers

The field-dependence of the charge photogeneration efficiency reduces the holographic contrast in an organic photorefractive composite. In this article, the Braun model for field-dependent photogeneration efficiency is incorporated into the standard model of photorefractivity. Using this formalism, the effect on the space-charge field, and thereby holographic index contrast, is calculated directly without the need for empirically found parameters. The dependence of the space-charge field on experimental geometry is also analyzed. A powerful description of the effective space-charge field is thus derived and is experimentally verified. This analysis is then used to compare the observed holographic contrast to that predicted from transmission ellipsometry measurements. (C) 2001 American Institute of Physics.