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Virtual Journal for Biomedical Optics

Virtual Journal for Biomedical Optics


  • Editors: Andrew Dunn and Anthony Durkin
  • Vol. 6, Iss. 7 — Jul. 27, 2011

Under-filling trapping objectives optimizes the use of the available laser power in optical tweezers

Mohammed Mahamdeh, Citlali Pérez Campos, and Erik Schäffer  »View Author Affiliations

Optics Express, Vol. 19, Issue 12, pp. 11759-11768 (2011)

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For optical tweezers, especially when used in biological studies, optimizing the trapping efficiency reduces photo damage or enables the generation of larger trapping forces. One important, yet not-well understood, tuning parameter is how much the laser beam needs to be expanded before coupling it into the trapping objective. Here, we measured the trap stiffness for 0.5–2 μm-diameter microspheres for various beam expansions. We show that the highest overall trapping efficiency is achieved by slightly under-filling a high-numerical aperture objective when using microspheres with a diameter corresponding to about the trapping-laser wavelength in the medium. The optimal filling ratio for the lateral direction depended on the microsphere size, whereas for the axial direction it was nearly independent. Our findings are in agreement with Mie theory calculations and suggest that apart from the choice of the optimal microsphere size, slightly under-filling the objective is key for the optimal performance of an optical trap.

© 2011 OSA

OCIS Codes
(000.2170) General : Equipment and techniques
(140.7010) Lasers and laser optics : Laser trapping
(180.0180) Microscopy : Microscopy
(350.4855) Other areas of optics : Optical tweezers or optical manipulation

ToC Category:
Optical Trapping and Manipulation

Original Manuscript: January 4, 2011
Revised Manuscript: March 4, 2011
Manuscript Accepted: March 20, 2011
Published: June 2, 2011

Virtual Issues
Vol. 6, Iss. 7 Virtual Journal for Biomedical Optics

Mohammed Mahamdeh, Citlali Pérez Campos, and Erik Schäffer, "Under-filling trapping objectives optimizes the use of the available laser power in optical tweezers," Opt. Express 19, 11759-11768 (2011)

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