Detection limits in whispering gallery biosensors with plasmonic enhancement

Abstract

We perform numerical modeling of a gold nanorod bound to the surface of a microtoroid-based biosensor. Localized surface plasmon resonances in the nanorod give rise to strong enhancements in the electric field when excited near resonance, increasing the frequency shift for a single bovine serum albumin molecule by a factor of 870, with even larger enhancements predicted for smaller proteins. On resonance, the frequency shift is predicted to be on the order of MHz, more than an order of magnitude larger than measurement noise arising from time-averaged frequency and thermal fluctuations.