Level repulsion in hybrid photonic-plasmonic microresonators for enhanced biodetection

TL;DR

This paper analyzes how coupling between photonic and plasmonic modes in hybrid microresonators can enhance biodetection sensitivity, highlighting the role of level repulsion and optimal detuning conditions.

Contribution

It provides a theoretical framework for understanding photonic-plasmonic interactions and introduces criteria for reactive versus resistive coupling in hybrid resonators.

Findings

Level repulsion enables sensitivity enhancement in WGM sensors.

Maximal enhancement occurs at half the plasmon linewidth detuning.

Bounds are established for possible sensitivity improvements.

Abstract

We theoretically analyse photonic-plasmonic coupling between a high Q whispering gallery mode (WGM) resonator and a core-shell nanoparticle. Blue and red shifts of WGM resonances are shown to arise from crossing of the photonic and plasmonic modes. Level repulsion in the hybrid system is further seen to enable sensitivity enhancements in WGM sensors: maximal when the two resonators are detuned by half the plasmon linewidth. Approximate bounds are given to quantify possible enhancements. Criteria for reactive vs. resistive coupling are also established.