Hybridized Plasmonic Modes in Semiconductor-Based Metasurfaces: A Gateway to Dual Fano Resonances

A metagrating structure comprising aluminum (AI) and gallium phosphide (GaP), along with a planar indium tin oxide (ITO) spacer on top of an Al substrate, is proposed to achieve dual Fano resonances in the absorption spectrum. Without GaP grating, the Fano resonance arises from the coupling between localized surface plasmon resonance (LSPR) mode in the Al grating and gap-surface plasmon resonance mode in the ITO layer. Introducing the GaP semiconductor grating between the Al grating and the ITO spacer excites a hybrid plasmonic waveguide resonance mode, which couples with the LSPR mode to produce another Fano resonance and enhance the absorption bandwidth within the shortwave infrared range.