9318948 Hayden Nonlinear optical (NLO) materials for photonic applications will be studied using a new method to measure the pressure dependence of the decay of NLO coefficients at various temperatures in guest- host, side-chain, and main-chain NLO polymers by in-situ second harmonic generation. By performing a systematic study of a barbituric acid derivative in a guest-host and side-chain form, the hypothesis that the relaxation of the second order NLO susceptibility in a guest-host system is associated with the motion of a single repeat unit will be tested. Finally, this study will extend the understanding of local polymer dynamics in glassy materials by measuring the compressibility of the free volume and pressure dependence of the shift factor. The activation volume determined from the pressure dependence of the shift factor will be related to the size of the "reorganizing units" postulated in the configurational entropy theory of Adam and Gibbs. %%% By studying the relaxation of NLO materials as a function of pressure, the volume associated with the reorientation of the NLO moiety will be determined. This will allow designers to develop higher stability next generation materials for photonic devices such as high-speed optical modulators, waveguide harmonic generators and optical switches.
