Electro-optic Effects of Pole d Polymer Films Doped with Mixed Organic Materials p-Nitroaniline and p-Dicyanobenzene

Abstract

Second harmonic generation (SHG) from a mixed organic crystal of p-nitroaniline (p-NA)and p-dicyanobenzene (p-DCB) molecules was observed by the powder method, although each single crystal does not show the macroscopic SHG activity. The mixture showed the maximum SHG efficiency at a certain mixing ratio. This SHG activity is due to a kind of epitaxial growth of the noncentrosymmetrically aligned p-NA molecules. In this paper, a waveguide modulator of a poled polymer film doped with these mixed materials of p-NA and p-DCB was fabricated and the electrooptic coefficient r33 was measured. When the concentration of mixed materials was equal to 15 wt%, the value of r33 becomes maximum at a mixing ratio p-DCB: p-NA =O.4: 1. It was 23 times larger than the p-NA only doped film. It was found that the enhancement effect of r33 value came about when in the polymer matrix p-NA and p-DCB molecules gathered to some extent and interacted with each other. On the contrary, this enhancement effect was not observed when p-NA and p-DCB molecules were dispersed monomolecularly, and the only p-NA was found to contribute to the electrooptic effect.