Particle tracking stereomicroscopy in optical tweezers: control of trap shape

Bowman, R., Gibson, G. and Padgett, M. (2010) Particle tracking stereomicroscopy in optical tweezers: control of trap shape. Optics Express, 18(11), pp. 11785-11790. (doi: 10.1364/OE.18.011785)

Abstract

We present an optical system capable of generating stereoscopic images to track trapped particles in three dimensions. Two-dimensional particle tracking on each image yields three dimensional position information. Our approach allows the use of a high numerical aperture (NA= 1.3) objective and large separation angle, such that particles can be tracked axially with resolution of 3nm at 340Hz. Spatial Light Modulators (SLMs), the diffractive elements used to steer and split laser beams in Holographic Optical Tweezers, are also capable of more general operations. We use one here to vary the ratio of lateral to axial trap stiffness by changing the shape of the beam at the back aperture of the microscope objective. Beams which concentrate their optical power at the extremes of the back aperture give rise to much more efficient axial trapping. The flexibility of using an SLM allows us to create multiple traps with different shapes.

• Item Type: Articles
• Additional Information: This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OE.18.011785. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Gibson, Dr Graham and Bowman, Dr Richard and Padgett, Professor Miles
• Authors: Bowman, R., Gibson, G., and Padgett, M.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Optics Express
• Publisher: Optical Society of America
• ISSN: 1094-4087
• ISSN (Online): 1094-4087
• Published Online: 19 May 2010
• Copyright Holders: Copyright © 2010 Optical Society of America
• First Published: First published in Optics Express 18(11):11785-11790
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher