| Abstract
| - Optical waveguide technologies have been identified for broadband applications related to fiber network,airborne, and space-based communications. Active waveguide technologies developed around nonlinear optical(NLO) dye/polymer-based electrooptic devices have distinct advantages over existing RF communications interms of cost, weight, size, bandwidth, and immunity to electromagnetic interference, but their ultimateapplicability may be governed by optical loss. Though much attention has been given to the influences of theNLO chromophore optical nonlinearity, geometry, concentration, and poling effects on the bulk materialnonlinearity and device performance, less attention has been directed at the effects of the component materialproperties and dye concentration on fundamental near-IR optical absorption. We investigate here the effectsof polymer structural variations within the Bisphenol A polycarbonate family on near-IR absorption behaviorof guest−host materials, holding the dye constant, over a range of dye concentrations. Solvatochromismplays an important role in the near-IR absorption loss of a particular NLO dye, (2-(3-cyano-4-{2-[5-(2-{4-[ethyl(2-methoxyethyl)amino]phenyl}vinyl)-3,4-diethylthiophen-2-yl]vinyl}-5,5-dimethyl-5H-furan-2-ylidene)malononitrile). Near-IR loss vs dye absorption spectral shifts can be understood in terms of dye−polymerinteraction energies within the context of Marcus' theory of polar contributions to initial and final electronicstate free energies. The peak shift behavior can be described by the solvent polarity function of the polymerhost, consistent with the Onsager continuum dielectric model. Analysis of the geometric parameters intrinsicto the generalized Kawski solvent polarity correlation suggests a more spherical dye shape can lead to reducednear-IR loss. The loss vs concentration results show that selection of a low-loss host polymer is a necessarybut insufficient condition for establishing acceptable loss in a doped NLO dye−polymer system.
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