A closer look at two-photon absorption, absorption saturation and nonlinear refraction in gold nanoclusters

Abstract

The optical properties of atomically-precise gold nanoclusters differ significantly from those of plasmonic gold nanoparticles, in both linear and nonlinear regimes. Here, we present a systematic study on the third-order nonlinear optical (NLO) properties of thiol-protected gold clusters in a wide range of wavelengths. We applied the Z-scan technique to evaluate the wavelength dispersion of two-photon absorption (2PA) and nonlinear refraction of the nanoclusters in water. The results are discussed with reference to 2PA of plasmonic gold nanoparticles and literature data on NLO properties of gold nanoclusters.