3D characterization of the forces in optical traps based on counter-propagating beams shaped by a spatial light modulator

Research output: Contribution to book/anthology/report/proceedingArticle in proceedingsResearchpeer-review

  • Martin Verner Gammelgaard Kristensen, Denmark
  • Thue Bjerring Lindballe, Denmark
  • Anton Paarup Kylling, Denmark
  • Darwin Palima, Terahertz Technologies and Biophotonics, Denmark
  • Jesper Glückstad, Terahertz Technologies and Biophotonics, Denmark
  • Søren Rud Keiding
  • Henrik Stapelfeldt
An experimental characterization of the 3D forces, acting on a trapped polystyrene bead in a counter-propagating beam geometry, is reported. Using a single optical trap with a large working distance (in the BioPhotonics Workstation), we simultaneously measure the transverse and longitudinal trapping force constants. Two different methods were used: The Drag force method and the Equipartition method. We show that the counterpropagating beams traps are simple harmonic for small displacements. The force constants reveal a transverse asymmetry as κ- = 9.7 pN/μm and κ+ = 11.3 pN/μm (at a total laser power of 2x35 mW) for displacements in opposite directions. The Equipartition method is limited by mechanical noise and is shown to be applicable only when the total laser power in a single 10 μm counter-propagating trap is below 2x20 mW.
Original languageEnglish
Title of host publicationSPIE Proceedings
Publication year2010
Publication statusPublished - 2010

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