Enhancement of second-harmonic generation in a one-dimensional periodic structure

Selection of electromagnetic modes in a 1-dimensional dielectric periodic structure with a defect in the central period, is used to obtain sharp resonances in the generation of second harmonic light. We have observed experimentally the enhancement of the nonlinear interaction in the vicinity of the defect when the second harmonic wave is excited for modes within the forbidden zone or stop band. We have also observed an enhancement near the band edge, where the group velocity approaches zero. These results are in agreement with an analysis that includes the interference effects arising from multiple reflections in the periodic structure.