Second-harmonic generation from arrays of symmetric gold nanoparticles

We show that second-harmonic light can be generated from a diffraction grating of gold nanoparticles with planar inversion symmetry. By measuring the angular distribution of second-harmonic light, we observe an effect in which the diffraction pattern of the grating is superimposed on the intrinsic second-harmonic radiation pattern of the nanoparticles. This result suggests that the second-harmonic generation may be used to study coherent nonlinear optical effects in symmetric as well as asymmetric metal nanoparticles.