Position clamping in a holographic counterpropagating optical trap

Richard Bowman, Alexander Jesacher, Gregor Thalhammer, Graham M. Gibson, Monika Ritsch-Marte, Miles J. Padgett

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)9908-9914
Number of pages7
JournalOptics Express
Volume19
Issue number10
DOIs
Publication statusPublished - 9 May 2011

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Fingerprint Dive into the research topics of 'Position clamping in a holographic counterpropagating optical trap'. Together they form a unique fingerprint.

Cite this