Second Harmonic Generation from a single nanoparticle
We have developed a highly sensitive setup allowing measuring the second harmonic generation (SHG) from single nanoobjects such as 150 nm gold nanoparticles. The specificity of this setup is that the particles are freezed in a gelatine matrix, preventing the modification of the local environment of the nanoparticle and therefore allowing investigating the intrinsic nonlinear properties of the single object. In a first step the sample is scanned in order to locate the nanoparticles and then both hyperpolarizability and polarization resolved measurements are performed. The obtained results are in very good agreement with both ensemble experiments on nanoparticles in solution and Finite Element Methods (FEM) simulation. This unprecedented convergence of a very high sensitivity and a numerical approach opens up new perspectives in the investigation of the nonlinear properties of plasmonic nanostructures.