Ultra-sharp plasmonic resonance in graphene-coated triangular arrays for high-precision sensing

A high-performance plasmonic sensor featuring a graphene-coated triangular array is presented that achieves an exceptional combination of spectral sharpness and sensitivity. The sensor design demonstrates an ultra-narrow full width half maximum (FWHM) of 0.52 nm, enabled by strong plasmonic field confinement from the triangular array’s sharp vertices, suppressing radiative losses and graphene’s unique damping of plasmon decay via its high charge-carrier mobility and conductivity. The finite element method (FEM) simulations yield a record Q-factor of 1211 and figure of merit (FOM) of 769 RIU⁻^¹ while maintaining 400 nm/RIU sensitivity across a broad refractive index range (1.0–2.0). The optimized geometry (400 nm periodicity, 5 nm Au thickness) efficiently excites surface plasmons in the visible-NIR (400–800 nm). Graphene-enhanced charge-density oscillations, combined with the array’s field confinement, enable a resolution of 1.3 × 10⁻⁵ RIU (at SNR=100), establishing this platform for sub-nanometer spectral resolution in molecular sensing.