Resonant exciton nonlinearities with spatial dispersion

Abstract
We have measured, using a tunable laser, the resonant second-harmonic generation produced by excitons in CdS and ZnO. We find that spatial-dispersion effects are very important in the harmonic generation, and that only by including them can the data be properly understood. A comparison of the magnitude and sign of the exciton nonlinear coefficient determined from our measurements is found to be in good agreement with theory.