Broadening the Plasmonic Spectral Range of Metallic Metasurfaces Using Dual-Material Arrays.

Plasmonic nanoparticles support localized surface plasmon resonances (LSPR), exhibiting broad spectral features determined by nanoparticle geometry and material. When periodically arranged, they enable diffractive modes linked to Rayleigh anomalies (RA). The coupling between LSPR and RA produces surface lattice resonances, which combine strong field confinement, enhanced scattering, and high resonance quality with broad applications in sensing and light emission. While monometallic arrays have been extensively studied, bimetallic systems remain largely unexplored. This work investigates checkerboard arrays of gold and aluminum nanoparticles and demonstrates broadband surface lattice modes arising from hybridization of their distinct plasmonic responses. Simulations and experiments show that gold and aluminum dipolar resonances couple via the same RA in the near-infrared, extending beyond aluminum's usual plasmonic range. This previously unreported mechanism opens new routes toward broadband, high-performance plasmonic arrays for sensing, photonics, and telecommunications.