Holographic index-contrast prediction in a photorefractive polymer composite based on electric-field-induced birefringence

The physical properties of a hologram written in a photorefractive polymer composite are predicted from a macroscopic model based on ellipsometry. An electric poling field increases the birefringence of the composite. The way that the bulk birefringence changes with the electric field is used to predict the holographic index contrast, and, by comparison with experiment, accurate deductions of the holographic space-charge field are made. A photorefractive polymer composite was used that contained 47.5 wt. % 1-(2'-Ethylhexyloxy)-2,5-dimethyl-4-(4 " nitrophenylazo)benzene electro-optic dye. When sinusoidal modulation in optical intensity is used with high contrast, the higher spatial harmonics of the modulation of the holographic space-charge field become important. The amplitude of the first-order modulation in the space-charge field is accordingly reduced by 13% relative to the predictions of the standard model of photorefractivity in the case of a high-saturation field. (C) 2000 Optical Society of America [S0740-3224(00)01803-8] OCIS codes: 260.1440, 160.5320, 160.5470, 190.5330, 210.4770.