Dual-mode surface-plasmon sensor based on bimetallic film

We propose a plasmonic structure, based on a silver-gold two-layered metallic film, where two surface plasmons (SPs) with equal propagation constants are excited simultaneously at different wavelengths. We show theoretically that the bimetallic film provides unique opportunities for manipulation of plasmons and optimization of the accuracy and cross-sensitivity. The structure can be used as an effective self-reference SP sensor in wavelength-interrogated design.