Creation of second-order nonlinearity in polymers by light-induced asymmetric charge injection.

A new method for creating and enhancing second-order optical nonlinearity in polymer-dye films by asymmetric photoinjection of electric charges is introduced. The samples are composed of two separate layers, an organic photoconductor that generates the electric charges and a hyperpolarizable organic film that traps them. The nonlinearity caused by asymmetric charge injection does not arise from dipolar alignment; consequently, it can be observed either in the absence of, or to enhance, the conventional dipolar alignment nonlinearity.