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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 15, Iss. 7 — Apr. 2, 2007
  • pp: 4359–4371

Optical trapping of director structures and defects in liquid crystals using laser tweezers

Ivan I. Smalyukh, Daniel S. Kaputa, Aliaksandr V. Kachynski, Andrey N. Kuzmin, and Paras N. Prasad  »View Author Affiliations

Optics Express, Vol. 15, Issue 7, pp. 4359-4371 (2007)

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We demonstrate optical manipulation of structures and defects in liquid crystals (LCs). The effective refractive index depends on the LC molecular orientations and the laser beam’s polarization. We use the orientation-mediated refractive index contrast for the laser trapping in LCs with a homogeneous composition, but with spatially-varying patterns of molecular orientations. Tightly-focused polarized beams allow for optical trapping of disclinations and their clusters, dislocations and oily streaks, cholesteric fingers and focal conic domains, etc. We calculate the optical gradient forces for typical structures and explain the trapping properties at low laser powers. We also show that when a high-power beam causes local molecular realignment, the laser trapping properties change for two reasons: (1) the refractive index pattern and optical gradient forces are modified; (2) additional elastic structural forces arise to minimize the elastic free energy.

© 2007 Optical Society of America

OCIS Codes
(140.7010) Lasers and laser optics : Laser trapping
(160.1190) Materials : Anisotropic optical materials
(160.3710) Materials : Liquid crystals
(180.6900) Microscopy : Three-dimensional microscopy
(260.1440) Physical optics : Birefringence

ToC Category:

Original Manuscript: December 21, 2006
Revised Manuscript: February 25, 2007
Manuscript Accepted: February 26, 2007
Published: April 2, 2007

Ivan I. Smalyukh, Daniel S. Kaputa, Aliaksandr V. Kachynski, Andrey N. Kuzmin, and Paras N. Prasad, "Optical trapping of director structures and defects in liquid crystals using laser tweezers," Opt. Express 15, 4359-4371 (2007)

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