Abstract

We have shown¹ that asymmetric injection of electric charge into polymer-dye blends can induce second-order nonlinear optical effects that are distinct from the more conventional mechanism of using electric fields to align the dye molecules. An in-plane geometry¹ can be used to inject charges into polymer-dye films, causing symmetry breakage both parallel and perpendicular to the external field. The symmetry breakage perpendicular to the field results from the setting up of a macroscopic charge gradient, whereas nonlinearity parallel to the field results from conventional dipolar alignment. For high voltages but only moderate fields (2000 V across 2 mm) charge injection effects can be stronger than dipolar alignment. It is believed that charged dimers and quadrupolar nonlinearities are responsible for the nonlinearity in a charge gradient.²

© 1995 Optical Society of America