Third Harmonic Generation Enhanced by Generalized Kerker Condition in All-Dielectric Metasurfaces

The abundant multipolar resonances in all-dielectric metasurfaces provide a new paradigm to simultaneously induce strong near-field confinement in the interior of a nanocavity as well as to manipulate the far-field scattering property, which is beneficial for the enhancement of nonlinear effects. Here, third-harmonic generation (THG) of all-dielectric silicon metasurfaces that sustain dominant electric dipole (ED), toroidal dipole (TD), and magnetic dipole (MD) moments in near-infrared is numerically and experimentally studied. The effect of the interplay of these resonant modes on THG is investigated, and a pronounced THG enhancement is observed when these modes become spectrally overlapped, corresponding to the generalized Kerker condition. The constructive interference of the total electric dipole (refers to the summation of the ED and TD scattered fields) and MD modes results in the suppression of the backward scattering along with a strong local-field enhancement inside the dielectric resonators. The simulation (experimental) results show a 214-fold (17-fold) THG enhancement in the vicinity of the generalized Kerker condition compared with the signals of the spectrally separated TD and MD resonances. The silicon-based metasurfaces with their simple geometry are facile for large-area fabrication and open new possibilities for the optimization of upconversion processes to achieve efficient nonlinear devices.