Excitation of dark plasmonic cavity modes via nonlinearly induced dipoles: applications tonear-infrared plasmonic sensing

Abstract

We demonstrate that dark plasmon modes of cavity-shaped plasmonic structures made ofmetallic nanowires can be excited by local dipoles induced via second-harmonicgeneration. The optical properties of these plasmonic cavity modes are thoroughlycharacterized by using a numerical method that provides a complete description of theoptical field at both the fundamental frequency and the second harmonic. Inparticular, we show that the optical properties of these plasmonic cavity modes arestrongly dependent on the geometry of the plasmonic cavity and the materialparameters of its constituents. This enhanced sensitivity of dark plasmonic cavitymodes to the surrounding dielectric environment can find applications in plasmonicsensing. Specifically, this novel approach to sensing reveals that detection limits of10 − 5 refractive index units can readily be achieved by using wavelength-sized plasmonic devices.