Detecting molecules with plasmonic resonators - Analytic expressions and bounds for the sensitivity and figure of merit

TL;DR

This paper derives analytical formulas for the sensitivity and figure of merit in plasmonic resonator-based refractive index sensing, revealing fundamental detection limits and guiding optimal resonator design for single molecule detection.

Contribution

It provides the first analytic expressions for sensitivity and figure of merit, clarifies their fundamental limits, and discusses optimal resonator parameters for enhanced detection.

Findings

Sensitivity depends on energy concentration within the resonator.

Figure of merit is determined by the ratio of real to imaginary permittivity.

Optimal resonance wavelength and shape enhance single molecule detection.

Abstract

We derive analytic expressions for the sensitivity and figure of merit for refractive index sensing with plasmonic resonators in the quasistatic limit. Based on these expressions the limits of detection and their origins are investigated. The critical role of limited energy concentration within the resonators surrounding is shown. The classical figure of merit is found to be solely dependent on the ratio of real to imaginary part of the resonators permittivity . Based on these findings we discuss the optimum resonance wavelength and resonator size and shape for single molecule detection.