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Advances in Holographic Optical Trapping

Abstract
Holographic optical trapping (HOT) is a technique for non-invasive dynamic anipulation of multiple microscopic objects, which has been used for many applications in the life sciences during the past decade. The technique uses holographic beam steering with a spatial light modulator (SLM) to direct light to the desired positions of optical traps. In many cases, the control of the optical intensity of the traps is impaired by imperfections in the SLM. This has limited the use of HOT for applications sensitive to variations in the trap intensities, such as optical force measurement (OFM). Also, the algorithms for optimization of holograms used in HOT are computationally demanding, and real-time manipulation with optimized holograms has not been possible. In this thesis, four different methods for improving the accuracy of holographic beam steering are presented, along with a novel application for the combination of HOT and position measurement. The control of trap intensities is improved by compensating for crosstalk between pixels, and for spatial variations of the phase response of the SLM; and by dumping a controlled amount of light to specified regions away from the traps. Variations in trap intensities occurring when updating the SLM with new holograms are suppressed by enforcing a stronger correlation between consecutive holograms. The methods consist of modifications of the algorithm used for hologram generation, or alternative methods for post-processing of generated holograms. Applications with high stability requirements, such as OFM with HOT, will benefit from the presented improvements. A method for reducing computation time for hologram optimization is also presented, allowing the accuracy improvements to be used also for time critical applications. Further, it is shown that position measurement of nanowires, held by multiple optical traps, can be used to probe the orientational structure and defects in liquid crystal materials.
Parts of work
I Minimizing intensity fluctuations in dynamic holographic optical tweezers by restricted phase change Martin Persson, David Engström, Anders Frank, Jan Backsten, Jörgen Bengtsson, and Mattias Goksör Optics Express, 18(11), 11250–11263, (2010). ::doi::10.1364/OE.18.011250
 
II Three-dimensional imaging of liquid crystal structures and defects by means of holographic manipulation of colloidal nanowires with faceted sidewalls David Engström, Rahul P. Trivedi, Martin Persson, Mattias Goksör, Kris A. Bertness and Ivan I. Smalyukh Soft Matter, 7, 6304–6312, (2011). ::doi::10.1039/C1SM05170A
 
III Real-time generation of fully optimized holograms for optical trapping applications Martin Persson, David Engström and Mattias Goksör Proceedings of SPIE, 8097, 80971H, (2011). ::doi::10.1117/12.893599
 
IV Unconventional structure-assisted optical manipulation of highindex nanowires in liquid crystals David Engström, Michael C.M. Varney, Martin Persson, Rahul P. Trivedi, Kris A. Bertness, Mattias Goksör, and Ivan I. Smalyukh Journal, 20(7), 7741–7748, (2012). ::doi::10.1364/OE.20.007741
 
V An algorithm for improved control of trap intensities in holographic optical tweezers Martin Persson, David Engström, Mattias Goksör Proceedings of SPIE, 8458, 84582W-1, (2012). ::doi::10.1117/12.930014
 
VI Reducing the effect of pixel crosstalk in phase only spatial light modulators Martin Persson, David Engström, and Mattias Goksör Optics Express, 20(20), 22334–22343, (2013). ::doi::10.1364/OE.20.022334
 
VII Calibration of spatial light modulators suffering from spatially varying phase response David Engström, Martin Persson, Jörgen Bengtsson, and Mattias Goksör Submitted to Optics Express April 2013.
 
Degree
Doctor of Philosophy
University
Göteborgs universitet. Naturvetenskapliga fakulteten
Institution
Department of Physics ; Institutionen för fysik
Disputation
Fredagen den 24 maj 2013, kl. 10.00, sal KC, Kemigården 4
Date of defence
2013-05-24
E-mail
martin.persson@physics.gu.se
URI
http://hdl.handle.net/2077/32606
Collections
  • Doctoral Theses / Doktorsavhandlingar Institutionen för fysik
  • Doctoral Theses from University of Gothenburg / Doktorsavhandlingar från Göteborgs universitet
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Thesis frame (25.07Mb)
Spikblad (251.4Kb)
Date
2013-05-05
Author
Persson, Martin
Keywords
Optical tweezers
Holographic optical trapping
Optical force measurement
Spatial light modulators
Holographic beam steering
Liquid crystals
Publication type
Doctoral thesis
ISBN
978-91-628-8697-4
Language
eng
Metadata
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