Size-dependent position of a single aerosol droplet in a Bessel beam trap

Thomas C. Preston, Bernard J. Mason, Jonathan P. Reid, David Luckhaus, Ruth Signorell

Research output: Contribution to journalArticle (Academic Journal)peer-review

24 Citations (Scopus)


The equilibrium position of an aerosol droplet trapped in a counter-propagating Bessel beam and gas flow is studied both experimentally and theoretically. This provides an aerosol analogue to the separation of particles of differing size and refractive index in counter-propagating laser beam and liquid flow, referred to as optical chromatography. Using the model system of a pure glycerol droplet it is found that, as evaporation takes place and the size of the droplet decreases, the size-dependent equilibrium position does not change in a simple monotonic fashion. Instead, the position of the droplet is greatly affected by the excitation of whispering gallery modes. This leads to sharp peaks in the equilibrium position curve, not unlike those that occur in single particle spectroscopy. The conditions necessary to excite whispering gallery modes are thoroughly investigated.

Original languageEnglish
Article number025702
JournalJournal of Optics
Issue number2
Publication statusPublished - 1 Feb 2014


  • aerosols
  • Bessel beam
  • optical chromatography
  • whispering gallery modes


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