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Thursday, November 26, 2009

Increasing trap stiffness with position clamping in holographic optical tweezers

Daryl Preece, Richard Bowman, Anna Linnenberger, Graham Gibson, Steven Serati, and Miles Padgett

We present a holographic optical tweezers system capable of position clamping multiple particles. Moving an optical trap in response to the trapped object’s motion is a powerful technique for optical control and force measurement. We have now realised this experimentally using a Boulder Nonlinear Systems Spatial Light Modulator (SLM) with a refresh rate of 203Hz. We obtain a reduction of 44% in the variance of the bead’s position, corresponding to an increase in effective trap stiffness of 77%. This reduction relies on the generation of holograms at high speed. We present software capable of calculating holograms in under 1ms using a graphics processor unit.

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