Far-field imaging of optical second-harmonic generation in single GaN nanowires.

Means for assessing the nonlinear optical properties of nanoscale materials are of key importance for the advancement of active nanophotonics. By correlating second-harmonic generation (SHG) with electron backscattered diffraction from single GaN nanowires (NWs), we demonstrate that far-field microscopic imaging of SHG offers an approach for distinguishing crystallographic orientations of NWs lying on a substrate. The quasi-static approximation, which should prove useful in describing many nanophotonic behaviors, is shown to satisfactorily account for the SHG data.