Enhanced second harmonic generation from supercavity mode and magnetic resonance in dumbbell-shaped silicon nanoblock

Abstract

Abstract Electromagnetic multipole resonance can be excited by dielectric nanostructures of appropriate size to effectively promote light-matter interaction. The interactions between light and nanostructures have the capability to enhance the electromagnetic near field, thereby improving the nonlinear effect of nanostructures. We illustrate that the supercavity mode and magnetic dipole (MD) resonance are activated by a single dumbbell-shaped silicon nanoblock, to trap the near-field electromagnetic field energy. Enhanced second harmonic generation (SHG) is achieved by exploiting the localized electromagnetic field at the surface of the nanostructure. Numerical simulations reveal that magnetic quadrupole (MQ) and total electric dipole (TED) can be coupled to the same radiation channel by adjusting continuously the aspect ratio L out/Ly (the outer edge length to the length of the nanoblock) of the nanoblock. When the aspect ratio L out/L y = 1, the supercavity mode formed by the interference of MQ and TED is excited at λ 1 = 1124 nm. And, the strong magnetic resonance mode formed by the coupling of two MDs in the same direction is also excited at λ 2 = 1248 nm. Supercavity mode and strong MD resonance can effectively capture electromagnetic fields on the surface of nanostructures to attain enhanced SHG. Our study presents a novel approach to enhance the nonlinear optical effect of a single silicon nanostructure, which can lead to the development of more efficient nonlinear optical devices.