Electrical control of optical plasmon resonance with graphene

ABSTRACT: Surface plasmon has the unique capability to concentrate light into subwavelength volume.1−5 Active plasmon devices using electrostatic gating can enable flexible control of the plasmon excitations,6 which has been demonstrated recently in terahertz plasmonic structures.7−9 Controlling plasmon resonance at optical frequencies, however, remains a significant challenge because gate-induced free electrons have very weak responses at optical frequencies.10 Here we achieve efficient control of near-infrared plasmon resonance in a hybrid graphene-gold nanorod system. Exploiting the uniquely strong11,12 and gate-tunable optical transitions13,14 of graphene, we are able to significantly modulate both the resonance frequency and quality factor of gold nanorod plasmon. Our analysis shows that the plasmon− graphene coupling is remarkably strong: even a single electron in graphene at the plasmonic hotspot could have an observable effect on plasmon scattering intensity. Such hybrid graphene−nanometallic structure provides a powerful way for electrical control of plasmon resonances at optical frequencies and could enable novel plasmonic sensing down to single charge transfer events