Generation of the second harmonic by a monolayer spherical double-layer nanoparticles

A model is proposed for calculating the intensity of the second harmonic (SH) when light is reflected from a monolayer consisting of a dielectric core and a plasmon shell of spherical nanoparticles located near the interface of two optically transparent media. The nonlinear polarization of the interface created by nanoparticles, which is the source of SH, is calculated. An increase in the intensity of the reflected SH caused by dipole and quadrupole plasmon resonances in nanoparticles was found. It is shown that the spectral positions of the SH intensity maxima depend significantly on the particle core size and its dielectric permittivity.