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

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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.