Gate-Tunable Spatial Modulation of Localized Plasmon Resonances

A. Arcangeli, F. Rossella, A. Tomadin, J. Xu, D. Ercolani, L. Sorba, F. Beltram, A. Tredicucci, M. Polini, and S. Roddaro

Nanoletters 16 (9), 5688-5693 (2016)
We demonstrate localization and field-effect spatial control of the plasmon resonance in semiconductor nanostructures, using scattering-type scanning near-field optical microscopy in the mid-infrared region. We adopt InAs nanowires embedding a graded doping profile to modulate the free carrier density along the axial direction. Our near-field measurements have a spatial resolution of 20 nm and demonstrate the presence of a local resonant feature whose position can be controlled by a back-gate bias voltage. In the present implementation, field-effect induces a modulation of the free carrier density profile yielding a spatial shift of the plasmon resonance of the order of 100 nm. We discuss the relevance of our electrically tunable nanoplasmonic architectures in view of innovative optoelectronic devices concepts.