Interferometric detection of mode splitting for whispering gallery mode biosensors

TL;DR

This paper introduces an interferometric method to detect hidden mode splitting in whispering gallery mode biosensors, enabling more practical detection of single particles or molecules in liquid environments.

Contribution

The paper presents a novel interferometric setup that reveals doublet spectral features obscured by resonance broadening, improving biosensor sensitivity in liquids.

Findings

Successful detection of hidden mode splitting in liquid environments

Enhanced sensitivity for nanoparticle and molecule detection

Potential for practical biosensor applications

Abstract

Sensors based on whispering gallery mode resonators can detect single nanoparticles and even single molecules. Particles attaching to the resonator induce a doublet in the transmission spectrum which provides a self-referenced detection signal. However, in practice this spectral feature is often obscured by the width of the resonance line which hides the doublet structure. This happens particularly in liquid environments that reduce the effective Q factor of the resonator. In this paper we demonstrate an interferometric set-up that allows the direct detection of the hidden doublet and thus provides a pathway for developing practical sensor applications.