Dispersion of the nonlinear susceptibility in gold nanoantennas

Abstract

Femtosecond optical pulses tunable in the near infrared are exploited to drive third harmonic generation (THG) and incoherent multiphoton photoluminescence (MPPL) in gold plasmonic nanoantennas. By comparing the yield of the two processes concurrently occurring on the same nanostructure, we extract the coherent third-order response of the antenna. Its contribution is enhanced at shorter excitation wavelengths allowing the observation of dispersion in the nonlinear susceptibility of gold.