Detection limits in plasmonic whispering gallery mode biosensors

TL;DR

This paper investigates how a metallic nanorod in a whispering gallery mode biosensor enhances detection sensitivity through localized surface plasmon resonance, predicting significant frequency shifts and detection limits.

Contribution

It introduces the analysis of plasmonic nanorods in whispering gallery mode biosensors, showing how they can drastically reduce mode volume and improve sensitivity.

Findings

Localized surface plasmon resonance enhances electric field

Optical frequency shifts up to 15 MHz predicted

Detection limited by laser frequency noise

Abstract

We analyze a whispering gallery mode biosensor with a metallic nanorod bound to its surface. It is found that a localized surface plasmon resonance in the nanorod can reduce the optical mode volume of the resonator by as much as four orders of magnitude via a local enhancement of the electric field, thus improving the detection sensitivity. Optical frequency shifts as large as 15 MHz are predicted for typical proteins and, for typical experimental parameters, the biosensor is predicted to be limited by laser frequency noise, leading to a minimum detectable polarizability on the order of 10 cubic angstroms.