Cavity-Coupled Plasmonic Device with Enhanced Sensitivity and Figure-of-Merit.

Using full-wafer processing, we demonstrate a sophisticated nanotechnology for the realization of an ultrahigh sensitive cavity-coupled plasmonic device that combines the advantages of Fabry-Perot microcavities with those of metallic nanostructures. Coupling the plasmonic nanostructures to a Fabry-Perot microcavity creates compound modes, which have the characteristics of both Fabry-Perot and localized surface plasmon resonance (LSPR) modes, boosting the sensitivity and figure-of-merit of the structure. The significant trait of the proposed device is that the sample to be measured is located in the substrate region and is probed by the compound modes. It is demonstrated that the sensitivity of the compound modes is much higher than that of LSPR of plasmonic nanostructures or the pure Fabry-Perot modes of the optical microcavity. The response of the device is also investigated numerically and the agreement between measurements and calculations is excellent. The key features of the device introduced in this work are applicable for the realization of ultrahigh sensitive plasmonic devices for biosensing, optoelectronics, and related technologies.

Coupling strength can control the polarization twist of a plasmonic antenna.

The far-field polarization of the optical response of a plasmonic antenna can be tuned by subtly engineering of its geometry. In this paper, we develop design rules for nano antennas which enable the generation of circular polarized light via the excitation of circular plasmonic modes in the structure. Two initially orthogonal plasmonic modes are coupled in such a way that a rotational current is excited in the structure. Modifying this coupling strength from a weak to a strong regime controls the helicity of the scattered field. Finally, we introduce an original sensing approach that relies on the rotation of the incident polarization and demonstrates a sensitivity of 0.23 deg·nm(-1) or 33 deg·RIU(-1), related to changes of mechanical dimensions and the refractive index, respectively.