Backward beam fanning in organic photorefractive devices

We observe strong beam depletion of about 30% at small incident angles in layered photorefractive polymers at an electric field of − 50 V ∕ μ m and an intensity of 0.3 W ∕ cm 2 . At normal incidence this depletion occurs only with negative electric field directions. For positive fields, depletion occurs only in the tilted geometry and is due to forward beam fanning, as previously observed. We attribute the depletion for negative electric fields mainly to the backward beam fanning as a consequence of the relatively high beam coupling efficiency in reflection grating geometries.