Dipolar Reorientation of a Nonlinear Optical Chromophore Doped in AmorphousPolymers Investigated by Electrochromism

摘要

The dynamics associated with the dipolar orientation of a nonlinear opticalchromophore, nitroaminostilbene (NAS), doped in three different polymer hosts, polymethylmethacrylate (PMMA), polycarbonate (PC) and poly(vinyl)chloride is investigated by an electrochromic technique. The relaxation of the electric field induced dipolar order is investigated as a function of temperature and dopant concentration. The time dependence of the electronic absorption spectrum perturbed by the electric field is measured. The relaxation time measured below the glass transition temperature (Tg) shows an Arrhenius dependence, with the activation energy increasing with increasing chromophore concentration. Measurements with three different polymer hosts below each system's Tg are carried out. At a given chromophore concentration, the relaxation time varies significantly from one polymer host to another. A pronounced memory effect in the relaxation time associated with increasing number of poling cycles has been observed in the NAS/PC system.