Measuring the hyperpolarizability beta in asymmetric molecules with quadratic electroabsorption.

摘要

In this dissertation we present various experiments, both linear and nonlinear in nature, designed to characterize nonlinear chromophores for optical device applications. We have also developed a direct deflection measurement procedure to determine the refractive index profile of polymer optical fiber preforms. We study five new nonlinear chromophores synthesized by the Chemistry Dept. at Washington State University with linear absorption and fluorescence measurements. From the fits we obtain transition energies and dipole transition moments which we then use in analyzing data obtained by quadratic electroabsorption (QEA) to determine the third-order bulk susceptibility. We have determined that in asymmetric molecules the molecular second-order susceptibility contributes significantly to the bulk third-order susceptibility. To analyze the data we apply inhomogeneous broadening theory to the three-level quantum expressions describing both the second- and third-order susceptibilities and show that it models the data better than Lorentzian theory. We present the results of fits for the QEA measurements under various cases of contributions from the molecular susceptibilities.