On-chip Single Nanoparticle Detection and Sizing by Mode Splitting in an Ultra-high-Q Microresonator

TL;DR

This paper demonstrates real-time detection and sizing of individual nanoparticles down to 30 nm using mode splitting in an ultra-high-Q microresonator, enabling label-free, single-shot measurements with high accuracy.

Contribution

The authors introduce a novel, label-free method for detecting and sizing single nanoparticles using mode splitting in a whispering-gallery-mode microresonator, achieving high resolution without prior particle information.

Findings

Successfully detected and sized 30 nm radius nanoparticles in real-time.

Achieved high noise suppression and single-shot measurement accuracy.

Provided a platform for studying nanoparticles at single particle resolution.

Abstract

The ability to detect and size individual nanoparticles with high resolution is crucial to understanding behaviours of single particles and effectively using their strong size-dependent properties to develop innovative products. We report real-time, in-situ detection and sizing of single nanoparticles, down to 30 nm in radius, using mode-splitting in a monolithic ultra-high-Q whispering-gallery-mode (WGM) microtoroid resonator. Particle binding splits a WGM into two spectrally shifted resonance modes, forming a self-referenced detection scheme. This technique provides superior noise suppression and enables extracting accurate size information in a single-shot measurement. Our method requires neither labelling of the particles nor apriori information on their presence in the medium, providing an effective platform to study nanoparticles at single particle resolution.