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.

Figure 1

(Color online). Experimental setup for measuring angular distribution of SH light. Inset: SEM image of “tilted” rods with 200 nm spacing.

Figure 2

(a) Polarization-dependent extinction from “straight” rods. (b) Angular distribution of the SHG for the two polarizations. All diffraction patterns are corrected for electrical dark and for the nonlinear response of the bare substrate.

Figure 3

(a) Polarization-dependent extinction from tilted rods. (b) Angular distribution of the SHG with varying lattice spacing. The signal from the 600-nm-spacing array is scaled by 0.36 to match the areal density of the $1\text{−}\mu \mathrm{m}$-spacing array.

Figure 4

(Color online) (a) Diagram of the SH dipole emission pattern. (b) Model calculation of 2(b). (c) Model calculation of 3(b).