Efficient Third Harmonic Generation by Doubly Enhanced Electric Dipole Resonance in Metal-Based Silicon Nanodisks

Abstract

Mie-type electric dipole resonance (EDR) is a commonly feasible Mie-type resonance in all-dielectric metasurfaces. However, conventional EDR suffers from the weak field enhancement and the poor field confinement inside the dielectric, resulting in an inefficient third harmonic generation (THG). Here, by presenting a bottom metal film and manipulating the array period, an effective perfect electric conductor (PEC) mirror effect and a novel coupling effect, as well as their successive combination, are proposed to doubly enhance the EDRs in silicon nanodisks and thus their THG at near-infrared. Numerical frequency and time domain responses demonstrate that the total THG conversion efficiency assisted by doubly enhanced EDR is raised by more than three and eight orders of magnitude compared to those of EDRs with only PEC effect and with a SiO $_2$ substrate, respectively. Furthermore, silicon Kerr effect, describing the field-dependent refractive index with third-order susceptibility, is analyzed under increasing pump intensity. An unprecedented efficiency ∼ $10^{-2}$ under pump intensity 2 GW/cm $^2$ is achieved despite the Kerr effect. This work paves a new way for engineering and boosting the Mie-type EDR, and facilitates its practical applications in quantum sources, spectroscopic and biochemical sensing.