Tailoring Third Harmonic Generation From Anapole Mode in a Metal-Dielectric Hybrid Nanoantenna

An all-dielectric nanoantenna is expected to greatly boost the nonlinear performance owing to its large mode volume and low material loss. However, it still suffers from the relatively weak near-field enhancement and the inferior far-field directivity. In this work, by successively introducing an upper metal ring and a bottom metal film, the plasmonic resonance and the perfect electric conductor (PEC) mirror effect are employed to significantly enhance and tailor the third harmonic generation (THG) from the high-index silicon nanoantenna. Numerical results show that benefiting from both of these two metal components, not only the THG efficiency is increased by more than 1 and 3.5 orders of magnitude compared with those with only single metal component and without any metal component, respectively, but also an improved radiation directivity can be obtained. The dependences of geometric parameters are discussed as well. This work suggests a route to enhance and manipulate the nonlinear radiation by a hybrid nanoantenna and facilitates its practical applications such as biosensing and nonlinear light sources.