title: Dependence of the Bragg condition on an external electric field for a polymeric photorefractive material.
abstract: We investigated the effect of an applied electric field on the Bragg condition of degenerate four-wave mixing a polymeric photorefractive material with a low glass-transition temperatue. For a polymeric photorefractive material the application of an external electric field is necessary for photorefractivity leads to birefringence of the material by poling of the nonlinear optical chromophore. Because the propagation vectors of the pumping and reading beams inside the material are influenced by the refractive index of the material, the Bragg condition depends on the magnitude of the external field. Using an oriented gas model and the-coupled-mode theory, we numerically analyzed the Bragg-mismatch effect that causes a reduction in diffraction efficiency as a function of an external field. We present the boundary conditions for sample thickness and grating spacing for which the Bragg-mismatch effect must be taken into account.
authors.affiliation: Department of Chemistry, Hanyang University, Seoul 133-791, Korea.
authors.forename: Won-Jae
authors.initials: WJ
authors.lastname: Joo
authors.forename: Hyunaee
authors.initials: H
authors.lastname: Chun
authors.forename: In Kyu
authors.initials: IK
authors.lastname: Moon
authors.forename: Nakjoong
authors.initials: N
authors.lastname: Kim