Enhancement of the molecular hyperpolarizability by a supramolecular amylose-dye inclusion complex, studied by hyper-Rayleigh scattering with fluorescence suppression

The first hyperpolarizability beta of a free hemicyanine dye and a homologue dye included in a supramolecular complex have been determined by hyper-Rayleigh scattering. Since the inclusion complex is fluorescent, high-frequency demodulation of the time-delayed multiphoton fluorescence has been used to retrieve a fluorescence-free inherent value for its first hyperpolarizability. The free dye does not exhibit fluorescence; the inclusion induces fluorescence with a lifetime of 4.8 +/- 0.1 ns; and the inclusion complex has a fluorescence-free value for its dispersion-free first hyperpolarizability beta(0) of approximately twice that for the free dye ((200 +/- 5) X 10(-30) vs. (100 +/- 10) X 10(-30) esu)). The enhanced polar orientation of this complex in thin films, and better thermal and mechanical stability, together with this increase in molecular nonlinearity confirm inclusion as a way to engineer efficient macroscopic arrangements for nonlinear optics. (C) 1998 Elsevier Science B.V. All rights reserved.