Modeling of a plasmonic nanosensor based on an open box-like metal cavity

Abstract

We propose a plasmonic nanosensor based on an open box-like metal nanocavity. Surface plasmon polaritons (SPPs) excited at the metal/dielectric interface oscillate in the cavity, and then, plasmonic resonance modes are formed. Since the cavity is open, a part of the resonance light of the SPPs is scattered to light. By monitoring the shift in the scattering spectrum, the refractive index change of the sensed material can be derived. Because of the high reflectivity of the metallic walls, the sensitivity and figure of merit (FOM) are higher than those using single nanoparticle or nanoantenna. A sensitivity of 1046 nm/RIU (RIU denotes refractive index unit) and a FOM of 23.4 are derived for a 700 nm long and 350 nm high square cavity. Furthermore, the sensing area of the proposed sensor is smaller than 1 μm² and the performance of the nanosensor can be further tuned by varying the cavity dimensions. The proposed sensor is well suited for observing small changes in biological and chemical reactions.

Keywords:

• surface plasmon polaritons
• surface plasmon resonance
• refractive index sensor
• plasmonic nanosensor
• nanocavity

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 61377050], [grant number 11574011]; the Research Fund for the Doctoral Program of Higher Education under [grant number 20130001110050].