Linear electrooptic effect in hemicyanine self-assembled monolayer on gold substrate

The linear electrooptic (EO) effect (Pockels effect) in a self-assembled monolayer (SAM) containing nonlinear optical chromophore of hemicyanine adsorbed on a gold surface was studied in the attenuated total reflection geometry (ATR) at various wavelengths under the surface plasmon resonance condition. Since a gold surface is EO active and the signal from the SAM is comparable with that from the gold surface, contribution from the gold surface should be removed in the analysis. The greatest second-order nonlinear susceptibility χ(2) of the SAM containing hemicyanine was found to be 65 pm V−1 at wavelengths of 612 and 635 nm. This value is comparable with the χ(2) measured by second-harmonic generation.