Nonlinear Optical Magnetism Revealed by Second-Harmonic Generation in Nanoantennas.

TLDR: This work distinguishes experimentally the contribution of electric and magnetic nonlinear response by analyzing the structure of polarization states of vector beams in the second-harmonic radiation and provides a direct observation of nonlinear optical magnetism through selective excitation of multipolar nonlinear modes in nanoantennas.

Abstract: Nonlinear effects at the nanoscale are usually associated with the enhancement of electric fields in plasmonic structures Recently emerged new platform for nanophotonics based on high-index dielectric nanoparticles utilizes optically induced magnetic response via multipolar Mie resonances and provides novel opportunities for nanoscale nonlinear optics Here, we observe strong second-harmonic generation from AlGaAs nanoantennas driven by both electric and magnetic resonances We distinguish experimentally the contribution of electric and magnetic nonlinear response by analyzing the structure of polarization states of vector beams in the second-harmonic radiation We control continuously the transition between electric and magnetic nonlinearities by tuning polarization of the optical pump Our results provide a direct observation of nonlinear optical magnetism through selective excitation of multipolar nonlinear modes in nanoantennas