Multiband Hybrid Metasurface for Enhanced Second-Harmonic Generation via Coupled Gap Surface Plasmon Modes

TL;DR

This paper introduces a multiband hybrid metasurface with coupled plasmon modes that enhances second-harmonic generation, offering tunable multiband operation for advanced nanophotonic applications.

Contribution

It presents a novel metal-dielectric-metal metasurface supporting multiple plasmon modes with optimized geometry for enhanced SHG across multiple bands.

Findings

Four distinct resonances achieved in near-infrared and telecom bands

Good agreement between experimental measurements and numerical simulations

Enhanced second-harmonic generation observed at resonance wavelengths

Abstract

A multiband hybrid metasurface supporting multiple gap-surface plasmon (GSP) and localized surface plasmon (LSP) modes is presented. The structure adopts a metal-dielectric-metal configuration consisting of an aluminum bottom layer, a silicon dioxide spacer, and a bar-disc hybrid resonator patterned in the top aluminum layer. Optimized geometrical parameters yield four distinct resonances across the near-infrared and telecommunication bands, arising from the interplay between GSP modes and LSP excitations. The reflectance spectra are systematically analyzed as functions of geometric parameters and polarization, demonstrating tunable multiband operation. Experimental measurements of the fabricated metasurface show good agreement with numerical predictions. Furthermore, the second-harmonic generation (SHG) response is numerically investigated, revealing enhanced SH emission at the resonance wavelengths due to strong electromagnetic field confinement within the metal-dielectric-metal cavity. The proposed metasurface provides a compact platform for multiband and multifunctional nanophotonic applications.