Second-Harmonic Generation by a Monolayer of Spherical Two-Layer Nanoparticles

A model for calculating the second-harmonic (SH) intensity at reflection of light from a monolayer of spherical nanoparticles consisting of a dielectric core and a plasmonic shell, which is located near the interface between two optically transparent media, is proposed. Nonlinear polarization of the interface created by nanoparticles (a source of the SH) is calculated. It is found that the intensity of the reflected SH increases due to the dipole and quadrupole plasmon resonances in nanoparticles. It is shown that the spectral positions of the SH intensity maxima depend strongly on size particle core and its permittivity.