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Use of shape induced birefringence for rotation in optical tweezersFormat | Member Price | Non-Member Price |
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Paper Abstract
Since a light beam can carry angular momentum (AM) it is possible to use optical tweezers to exert torques to twist or
rotate microscopic objects. The alignment torque exerted on an elongated particle in a polarized light field represents a
possible torque mechanism. In this situation, although some exchange of orbital angular momentum occurs, scattering
calculations show that spin dominates, and polarization measurements allow the torque to be measured with good
accuracy. This phenomenon can be explained by considering shape birefringence with an induced polarizability tensor.
Another example of a shape birefringent object is a microsphere with a cylindrical cavity. Its design is based on the fact
that due to its symmetry a sphere does not rotate in an optical trap, but one could break the symmetry by designing an
object with a spherical outer shape with a non spherical cavity inside. The production of such a structure can be achieved
using a two photon photo-polymerization technique. We show that using this technique, hollow spheres with varying
sizes of the cavity can be successfully constructed. We have been able to demonstrate rotation of these spheres with
cylindrical cavities when they are trapped in a laser beam carrying spin angular momentum. The torque efficiency
achievable in this system can be quantified as a function of a cylinder diameter. Because they are biocompatible and
easily functionalized, these structures could be very useful in work involving manipulation, control and probing of
individual biological molecules and molecular motors.
Paper Details
Date Published: 28 August 2010
PDF: 8 pages
Proc. SPIE 7762, Optical Trapping and Optical Micromanipulation VII, 77621C (28 August 2010); doi: 10.1117/12.861793
Published in SPIE Proceedings Vol. 7762:
Optical Trapping and Optical Micromanipulation VII
Kishan Dholakia; Gabriel C. Spalding, Editor(s)
PDF: 8 pages
Proc. SPIE 7762, Optical Trapping and Optical Micromanipulation VII, 77621C (28 August 2010); doi: 10.1117/12.861793
Show Author Affiliations
Theodor Asavei, The Univ. of Queensland (Australia)
Timo A. Nieminen, The Univ. of Queensland (Australia)
Timo A. Nieminen, The Univ. of Queensland (Australia)
Norman R. Heckenberg, The Univ. of Queensland (Australia)
Halina Rubinsztein-Dunlop, The Univ. of Queensland (Australia)
Halina Rubinsztein-Dunlop, The Univ. of Queensland (Australia)
Published in SPIE Proceedings Vol. 7762:
Optical Trapping and Optical Micromanipulation VII
Kishan Dholakia; Gabriel C. Spalding, Editor(s)
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