Enhancement of Third-Harmonic Generation Through Plasmonic Gap and Cavity Resonance Modes in Bilayer Graphene/Dielectric/Graphene Metasurfaces

This study presents a technique for achieving high third-harmonic generation (THG) conversion efficiency using a bilayer graphene/dielectric/graphene metasurface structure in the terahertz (THz) range. The enhanced THG mechanism leverages gap- and cavity-plasmon resonances at the resonant frequency, leading to effective localization and significant amplification of the electromagnetic (EM) wave on the graphene surface and within the gap region. This is due to the induction of both gap- and cavity-plasmon resonances. Introducing a metallic substrate beneath the bilayer structure narrows the resonant response bandwidth, resulting in zero transmittance and forming oscillating Fabry-Pérot (FP) waves within the cavity. This field enhancement, combined with graphene’s high nonlinear conductivity, boosts the THG conversion efficiency (CE) by several orders of magnitude, achieving − 24.905 dB at relatively low fundamental frequency (FF) input intensities. This device holds promise for various nonlinear optics and THz-integrated circuit applications, including terahertz switches and modulators.