Force measurement and optical assisted particle separation in an optical standing wave

W. Mu*, Z. Li, L. Luan, P. West, H. Kyriazes, G. C. Spalding, G. Wang, A. Feinerman, J. B. Ketterson

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations


We have measured the optical force on isolated particles trapped in an optical lattice generated by the interference of two coherent laser beams by a method based on the equipartition theorem and by an independent method based on hydrodynamic-drag. The experimental results show that the optical force on a particle in this type of optical lattice depends strongly on the ratio of the particle diameter to the period of the lattice. By tuning this ratio, the force due to the optical lattice can be made to vanish. We also formed optical lattices involving two independent standing waves with different spatial periods formed by tightly focusing four laser beams which are pair wise coherent. By shifting the relative phases of the interfering beams we can advance the two waves in opposite directions. Depending on the spacing and the translation speed of the two interference patterns, appropriately sized particles can be translated in opposite directions; using this approach we succeeded in separating two different sizes of particles in the presence of a simulated fluid flow.

Original languageEnglish (US)
Title of host publicationOptical Trapping and Optical Micromanipulation IV
StatePublished - 2007
EventOptical Trapping and Optical Micromanipulation IV - San Diego, CA, United States
Duration: Aug 26 2007Aug 29 2007

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherOptical Trapping and Optical Micromanipulation IV
Country/TerritoryUnited States
CitySan Diego, CA


  • Interferometer
  • Mie scattering
  • Optical trapping
  • Particle separation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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