Electro-optic effect in crystalline films of transverse planar octupolar symmetry

We present theoretical and experimental demonstrations of the electro-optic activity in crystalline molecular thin films with octupolar D_3h symmetry. Applying a longitudinal electric field modulation within the molecular plane, we analyze the induced refractive index change relative to the orientation of the octupoles in their plane, and show that a maximum value is reached when one octupolar branch lies along the direction of the modulating field. These characteristics, as well as their electric field dependence, are drastically different from more traditional one-dimensional symmetry samples, bringing additional advantages related to electro-optic coupling possibilities.