Robust enhancement of high-harmonic generation from all-dielectric metasurfaces enabled by polarization-insensitive bound states in the continuum

TL;DR

This paper demonstrates a robust method to enhance high-harmonic generation in all-dielectric metasurfaces using bound states in the continuum, achieving high efficiency and polarization insensitivity for nonlinear nanophotonic applications.

Contribution

It introduces a polarization-insensitive, high-Q quasi-BIC resonance in all-dielectric metasurfaces that significantly boosts harmonic generation efficiency.

Findings

Record high third-harmonic generation efficiency of 3.9×10⁻⁴ W⁻²

Record high fifth-harmonic generation efficiency of 4.8×10⁻¹⁰ W⁻⁴

Achieved polarization-insensitive nonlinear enhancement with moderate pump intensity

Abstract

The emerging all-dielectric platform exhibits high-quality ($Q$) resonances governed by the physics of bound states in the continuum (BIC) that drives highly efficient nonlinear optical processes. Here we demonstrate the robust enhancement of third-(THG) and fifth-harmonic generation (FHG) from all-dielectric metasurfaces composed of four silicon nanodisks. Through the symmetry breaking, the genuine BIC transforms into the high-$Q$ quasi-BIC resonance with tight field confinement for record high THG efficiency of $3.9\times10^{-4}$ W$^{-2}$ and FHG efficiency of $4.8\times10^{-10}$ W$^{-4}$ using a moderate pump intensity of 1 GW/cm$^{2}$. Moreover, the quasi-BIC and the resonantly enhanced harmonics exhibit polarization-insensitive characteristics due to the special $C_{4}$ arrangement of meta-atoms. Our results suggest the way for smart design of efficient and robust nonlinear nanophotonic devices.