Dark plasmonic modes in diatomic gratings for plasmoelectronics

Owing to the unique ability of nanostructured metals to confine and enhance light waves along metal-dielectric interfaces, plasmonics has enabled unprecedented flexibility in manipulating light at the deep-subwavelength scale. With regard to the spectral behavior of plasmonic resonances, the spectral location of a resonance can be tailored with relative ease while the control over the spectral linewidth represents a more daunting task. In this paper, we present sharp resonance features by introducing dark plasmonic modes in diatomic gratings. The induced asymmetry in the metallic structure facilitates the generation of a dark mode with significantly suppressed radiative loss leading to an ultra-sharp spectral feature similar to 5 nm wide. We further use this metallic structure as an optoelectronic platform for the transduction of light waves to electrical signals via a plasmoelectric effect. The light concentrating ability of dark plasmonic modes, in conjunction with the ultra-sharp resonance feature at a relatively low loss offers a novel route to enhanced light-matter interactions with high spectral sensitivity for diverse applications.