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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.

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The formation of pairs of perfect absorption associated with phase singularities in the parameter space using the hybridized structure constructed with a metallic nanoparticle array and a metallic film is promising to enhance light-mater interactions. However, the localized plasmon resonances of the array possess strong radiative losses, which is an obstacle to improve the performances for many applications. On the contrary with the subwavelength array hybridized structure, this study shows that by enlarging the lattice spacing, the oscillator strength of the nanoparticles can be enhanced with the formation of surface lattice resonance, thereby leading to similar but much narrower pairs of perfect absorption due to the interactions with the Fabry-Pérot cavity modes. Furthermore, when the surface plasmon polariton mode shift to the same spectral range associated with the enlarged lattice spacing, the coupling and mode hybridization with the surface lattice resonance result in an anticrossing in the spectra. Although the resonance coupling does not enter the strong coupling regime, the quality factors (∼ 134) and near-field enhancements (∼ 44) are strongly enhanced for the hybridized resonance modes due to the effectively suppressed radiative losses compared with that of the localized plasmon resonances, which make the hybridized structure useful for the design of functional nanophotonic device such as biosensing, multi-model nanolasing, and high-quality imaging.

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