Chromophore orientation dynamics, phase stability, and photorefractive effects in branched azobenzene chromophores

The increased solubility and uniform dispersal of branched azobenzene chromophores over their monomeric analogues have been shown to improve the electrooptic performance of high glass transition temperature (T-g) blended polymers. We report here the application of these branched chromophores as guest nonlinear optical molecules in the plasticized low-T-g photoconducting host polymer poly(vinylcarbazole) and demonstrate the presence of orientationally enhanced photorefractive index gratings. When compared with their monomeric analogues, branched chromophores were compatible over a broader range of concentrations and resulted in higher quality optical films; these films have retained their optical clarity for I year. A new branched electrooptic chromophore with r(33) of 14 pm/V at 1550 nm was synthesized and exhibited photorefractive two-beam coupling over a range of applied fields, including a net two-beam coupling amplification coefficient of 6.4 cm(-1) at 780 nm.