Photorefractive composite materials with bi-functional charge transporting second-order nonlinear optical chromophores

Abstract

Two bi-functional chromophores have been developed which possess second-order nonlinear optical and charge transporting properties. The second-order nonlinearity arises from conjugated structures terminated by donor and acceptor groups and the charge transporting property results from a triphenylamine moiety. The bi-functionality of the chromophores is confirmed by the large electro-optic coefficients and high photoconductivities of composites containing these chromophores. These chromophores have been incorporated into an inert polymer to form photorefractive composite materials when doped with a photocharge generation sensitizer. The electro-optic coefficients and photoconductivity of these composites have been measured as a function of the applied electric field as well as of the chromophore concentration. The dependence of the four-wave mixing diffraction efficiency, holographic grating writing rate, and two-beam coupling gain on the applied electric field and on the chromophore concentration have been evaluated. A quantitative relationship between the chromophore concentration and a number of photorefractive parameters including electro-optic coefficient, photoconductivity, four-wave mixing diffraction efficiency, and grating writing rate has been established.