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On-chip single nanoparticle detection and sizing by mode splitting in an ultrahigh-Q microresonator

A Corrigendum to this article was published on 01 February 2010

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The ability to detect and size individual nanoparticles with high resolution is crucial to understanding the behaviour 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 ultrahigh-quality-factor (Q) whispering-gallery-mode microresonator. Particle binding splits a whispering-gallery mode into two spectrally shifted resonance modes, forming a self-referenced detection scheme. This technique provides superior noise suppression and enables the extraction of accurate particle size information with a single-shot measurement in a microscale device. Our method requires neither labelling of the particles nor a priori information on their presence in the medium, providing an effective platform to study nanoparticles at single-particle resolution.

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Figure 1: Experimental set-up and coupled microtoroid cavity–nanoparticle system.
Figure 2: Transmission spectra and the amount of splitting versus number of deposited particles.
Figure 3: Illustration of mode splitting induced by a single nanoparticle in a microtoroid.
Figure 4: Single particle sizing using mode splitting (MS) in a microtoroid resonator.

Change history

  • 08 January 2010

    In the version of this Letter originally published, The scale bars of the scanning-electron microscope images in Fig. 1 were incorrect: the scale for Fig. 1a should have been 10 μm, and the scale for Fig. 1d should have been 5 μm. In Fig. 2b, the scale of the principal y-axis was incorrect and should have been x10−7. The unit of the y-axis for the inset figure remains as x10−8. These errors have been corrected in the HTML and PDF versions.


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This work was partially supported by MAGEEP (McDonnell Academy Global Energy and Environment Partnership) and CMI (Center for Materials Innovation) at Washington University in St. Louis.

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Authors and Affiliations



J.Z., S.K.O., L.Y. and D.R.C. designed the experiments and discussed the results and implications. J.Z., S.K.O. and Y.F.X. contributed to the theoretical work. J.Z. conducted the experiments. L.L. and L.H. prepared materials for the experiments. L.Y. and Y.F.X. conceived the experiments. All authors contributed to the writing of the paper. L.Y. and D.R.C. supervised and coordinated the project.

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Correspondence to Lan Yang.

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The authors declare no competing financial interests.

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Zhu, J., Ozdemir, S., Xiao, YF. et al. On-chip single nanoparticle detection and sizing by mode splitting in an ultrahigh-Q microresonator. Nature Photon 4, 46–49 (2010).

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