Chromophore Motion in Polymers for Nonlinear Optics by Solid-State NMR.
Technical rept. no. 2, 1 Mar-30 Nov 91,
TEXAS A AND M UNIV COLLEGE STATION DEPT OF CHEMISTRY
Pagination or Media Count:
There is much current interest in polymer materials for nonlinear optical NLO applications. These materials are commonly prepared by either dissolving doping a suitable NLO chromophore into a glassy or liquid crystalline polymer, or by covalently attaching the chromophore to the polymer host either by direct synthesis or radiative crosslinking. Regardless of the method of preparation, macroscopic orientation of the chromophore must be induced and maintained for efficient second-harmonic generation SHG in frequency doubling applications. For the most common use of a glassy polymer host, chromophore orientation is achieved by the process of poling. Briefly, the material is heated above Tg, a strong electric field is applied to orient the chromophores, and the material is cooled below Tg to lock in the orientation before the field is removed. A major problem in polymeric NLO materials is loss of SHG properties over time. For example, in a study of 4-dimethylamino-4-nitrostilbene in PMMA, Hampsch and coworkers reported that up to 80 of the SHG efficiency was lost after 12 h at 298 K.
- Electrical and Electronic Equipment