Journal of Physical Chemistry

Photorefractive polymers based on dual-function dopants

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A new class of photorefractive polymeric materials is described on the basis of inert polymer binders doped with a single small molecule species which has the dual function of providing both charge transport and optical nonlinearity, in order to maximize the volume fraction of both functionalities. A variety of compositions are investigated, using combinations of seven different dual function dopants, four different polymer binders, and two different sensitizing agents. The diffraction efficiency and characteristic response times of the observed gratings depend on the identity of the dual-function dopant as well as the binder polymer. In contrast to previous photorefractive polymers, mobility plays an important role in determining the response times of these materials. The increased concentration of the nonlinear optical chromophore which can be achieved leads to improved performance. Diffraction efficiencies as high as 7%, grating growth times of 0.43 s, and net two-beam coupling gain coefficients of 34 cm1 are observed in the polymer PMMA (poly(methyl methacrylate)):DTNBI (1,3-dimethyl-2,2-tetramethylene 5-nitrobenzimidazoline):C60.