Abstract

Besides the usual thermal assisted poling procedure the photoassisted poling reported for polymers containing azobenzene chromophores is of current interest. Usually the enhanced orientational mobility under illumination with visible light in the absorption band of the chromophore is explained by the trans⇔cis isomerization cycle of the azo dye, with a photoisomerization trans⇒cis and a thermal relaxation cis⇒trans. Because of the more compact shape of the cis isomer the rotational mobility is much higher than that of the trans isomer, thus polar orientation under electric DC field is possible. Since the memory of the polar orientation is lost only partially during the cis⇒trans transition, the trans isomers will achieve also a polar ordering [1-4]. This theory cannot be applied to systems containing stilbene dyes, where no thermal cis⇒trans relaxation is present. Investigations on systems containing stilbene dyes have also shown enhanced polar order in a poling process under illumination with visible light in the absorption range of the chromophore [5,6]. Thus the influence of heating of the sample (both macroscopically and microscopically in the vicinity of the dye molecule) must be discussed. The aim of this work is to compare the photoassisted poling behaviour of azo and stilbene dyes as well as of a non isomerizable biphenyl dye.

© 1995 Optical Society of America