Resonant Asymmetric All-Dielectric Metasurface for Boosting Third-Harmonic Generation

TL;DR

This paper demonstrates how breaking symmetry in silicon nanopillars creates sharp Fano resonances in dielectric metasurfaces, significantly boosting third-harmonic generation through enhanced optical intensity.

Contribution

It introduces a novel method of symmetry breaking to achieve high-Q resonances in dielectric metasurfaces, enabling efficient nonlinear optical processes.

Findings

Sharp Fano resonance achieved by symmetry breaking

Inverse quadratic relation between Q-factor and asymmetry

Enhanced third-harmonic generation demonstrated experimentally

Abstract

Resonant metasurfaces have received extensive attention due to their sharp spectral feature and extraordinary field enhancement. In this work, by breaking the in-plane symmetry of silicon nanopillars, we achieve a sharp Fano resonance. The far-field radiation and near-field distribution of metasurfaces are calculated and analyzed to further uncover the resonant performance of metasurfaces. Moreover, the theoretical derivation and simulation exhibit an inverse quadratic dependence of Q-factors on asymmetry parameters, revealing that the resonance is governed by the symmetry-protected bound states in the continuum. Finally we experimentally demonstrate the sharp resonance, and employ it to effciently boost the third-harmonic generation. This enhancement can be attributed to the strong optical intensity enhancement inside the metasurface.