Poling Dynamics and Effects of Trapped Charge in Poled Polymer Films for Nonlinear Optical Applications.
Abstract
The behavior of surface and trapped charge that originates during contact electric field poling of think films of optically nonlinear polymers has been investigated. Thin films of polymethylmethacrylate doped with two different tricyanothiophene chromophores have been studied during and after the poling process by simultaneous measurement of the current through the poling circuit and the second harmonic generation signal (SHG) from the polymer system. The poling current present in a fresh sample was found to differ in both magnitude and temporal dependence to that observed in the sample during subsequent polings. The magnitude of the steady state current eventually reached during the poling process was found to depend on temperature and was related to the mobility of charge. A sharp drop off in SHG signal intensity occurring when the poling electrodes were grounded is considered to be due to the removal of surface charge that orients chromophore dipoles near the surface of the film; the decay in the macroscopic polarization that the occurs is prolonged by charges trapped in the polymer matrix. The build-up of trapped charge explains a memory effect in which the SHG signal relaxation time gradually increased as the film was subjected to multiple polings. Finally, it is demonstrated that the release of charges trapped in the polymer matrix depends upon the heating rate and continues for above the glass transition temperature of the polymer.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 30, 1996
- Accession Number
- ADA307793
Entities
People
- Alex K. Jen
- C. H. Wang
- M. A. Pauley
Organizations
- University of Nebraska-Lincoln Department of Chemistry