Abstract
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.
Highlights
Optical tweezers are a technique by which the user can hold and manipulate micron sized particles for use in a range of experimental procedures
Image analysis and feedback control were performed in LabVIEW running on a quad core computer, which contained the graphics processor used for hologram calculation
It is important to distinguish the addressing rate of the spatial light modulator (SLM) and the speed with which a beam can be steered in practice
Summary
Optical tweezers are a technique by which the user can hold and manipulate micron sized particles for use in a range of experimental procedures They rely on the optical gradient force created when a tightly focused laser beam is incident on a dielectric particle, pulling it towards the local maxima of intensity [1]. Holographic optical tweezers (HOT) take this further by using a spatial light modulator (SLM) to dynamically split and control the laser beam [2] By this method, multiple optical traps may be created and manipulated in arbitrary 3D configurations without time-sharing [3], over tens of microns in the lateral and axial directions [4]
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