Position clamping in a holographic counterpropagating optical trap

Bowman, R., Jesacher, A., Thalhammer, G., Gibson, G. , Ritsch-Marte, M. and Padgett, M. (2011) Position clamping in a holographic counterpropagating optical trap. Optics Express, 19(10), pp. 9908-9914. (doi: 10.1364/OE.19.009908)

Abstract

Optical traps consisting of two counterpropagating, divergent beams of light allow relatively high forces to be exerted along the optical axis by turning off one beam, however the axial stiffness of the trap is generally low due to the lower numerical apertures typically used. Using a high speed spatial light modulator and CMOS camera, we demonstrate 3D servocontrol of a trapped particle, increasing the stiffness from 0.004 to 1.5μNm⁻¹. This is achieved in the “macro-tweezers” geometry [Thalhammer, J. Opt. 13, 044024 (2011); Pitzek, Opt. Express 17, 19414 (2009)], which has a much larger field of view and working distance than single-beam tweezers due to its lower numerical aperture requirements. Using a 10×, 0.2NA objective, active feedback produces a trap with similar effective stiffness to a conventional single-beam gradient trap, of order 1μNm⁻¹ in 3D. Our control loop has a round-trip latency of 10ms, leading to a resonance at 20Hz. This is sufficient bandwidth to reduce the position fluctuations of a 10μm bead due to Brownian motion by two orders of magnitude. This approach can be trivially extended to multiple particles, and we show three simultaneously position-clamped beads.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Gibson, Dr Graham and Bowman, Dr Richard and Padgett, Professor Miles
• Authors: Bowman, R., Jesacher, A., Thalhammer, G., Gibson, G., Ritsch-Marte, M., 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: 05 May 2011
• Copyright Holders: Copyright © 2011 Optical Society of America
• First Published: First published in Optics Express 19(10):9908-9914
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
56618	1	Optical Tweezers at Long Range and High Pressure (Creativity @ Home)	Miles Padgett	Engineering & Physical Sciences Research Council (EPSRC)	EP/I034726/1	Physics and Astronomy