Second-harmonic generation with metal/dielectric/metal hybridized nanoantennas: enhanced efficiency, reduced mode volume and ideal magnetic/electric dipole scattering

Although nonlinear optical responses with high refractive index dielectric nanostructures benefit from the large mode volume of the Mie resonances, it is an obstacle to achieve ultra-compact devices compared with plasmonic nanostructures. Besides that, the nonlinear emissions for dielectric nanoparticles often possess complex multipolar contributions, which is not favorable for nonlinear far-field manipulating such as beam steering. This study numerically demonstrates that with the formation of mode-matching condition, the efficiency of second-harmonic generation with an Au/AlGaAs/Au hybridized sandwich nanodisk can be enhanced by two orders compared with a same size AlGaAs nanoparticle, and the mode volume is reduced by about two orders at the same time. What is more interesting is that the nonlinear sources and far-field scattering are tailored by the hybridized resonances, where an ideal magnetic (or electric) dipole scattering around a broadband spectral range is observed for the second-harmonic generation, which provides a reliable way to generate pure magnetic light and to manipulate the nonlinear far-field emissions. The realization of enhanced nonlinear efficiency, the reduced mode volume, the background-free responses, and the ideal magnetic/electric dipole scattering make the sandwich hybridized nanoparticle a promising platform for nonlinear nanophotonics.