Adaptive optics in an optical trapping system for enhanced lateral trap stiffness at depth

Müllenbroich, M.C. , McAlinden, N. and Wright, A.J. (2013) Adaptive optics in an optical trapping system for enhanced lateral trap stiffness at depth. Journal of Optics, 15(7), 075305. (doi: 10.1088/2040-8978/15/7/075305)

Abstract

In optical trapping systems the trap stiffness, or spring constant, deteriorates dramatically with trap depth due to optical aberrations and system misalignment. This can severely hamper studies that employ optical tweezers to make accurate quantitative measurements. Here, a deformable membrane mirror is used, in conjunction with a random search algorithm, to correct for these aberrations by optimizing on a merit factor that is directly proportional to the trap stiffness. Previous studies have sought to address this issue but none have used a merit factor that is directly proportional to the trap stiffness. We demonstrate that the lateral trap stiffness, measured with and without aberration correction at increasing depths, improves throughout the trapping range of a conventional trap and allows us to extend the maximum depth at which we can trap from 136 to 166 μm. At a depth of 131 μm, trap stiffness improved by factors of 4.37 and 3.31 for the x- and y-axes respectively. The aberration correction resulted in deformable membrane mirror shapes where a single shape could be applied throughout a wide range of trap depths, showing significant improvement, and had the added benefit of making the lateral trapping forces more uniform in x and y.

• Item Type: Articles
• Additional Information: AJW acknowledges funding from EPSRC and the Royal Academy of Engineering and MCM from the Scottish University Physics Alliance (SUPA) prize studentship. Preliminary work was supported under the EU ACCORD scheme in collaboration with Imagine Optic.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Muellenbroich, Dr Caroline
• Authors: Müllenbroich, M.C., McAlinden, N., and Wright, A.J.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Journal of Optics
• Publisher: IOP Publishing
• ISSN: 2040-8978
• ISSN (Online): 2040-8986
• Published Online: 02 July 2013
• Copyright Holders: Copyright © 2013 IOP Publishing Ltd.
• First Published: First published in Journal of Optics 15(7): 075305
• Publisher Policy: Reproduced under a Creative Commons License