Dipolar Orientational Relaxation in Guest/Host Amorphous Polymer Probed by Second Harmonic Generation.

摘要

The decay of the second harmonic signal of a nonlinear optical chromophore dispersed in an amorphous polymer matrix is investigated. The decay curve can be fit either to the Kohrausch-Williams-Watts (KWW) stretched exponential function or to a bi-exponential function. The bi-exponential fit gives a better description of the decay of the second order nonlinear optical susceptibility of the contact electrode poled amorphous NLO polymer film. The fast decay component of the relaxation curve is attributed to the combined effect of reorientation of NLO dipole and the third order optical nonlinearity. The slow decay is due to the rotational diffusion of the NLO dipole. The temperature dependence of the rotational relaxation time is found to follow the Vogel-Fulcher-Tamman equation.