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Proceedings Paper

Measurement of angular momentum flux in optical tweezers
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Paper Abstract

It is well established that a light beam can carry angular momentum and therefore when using optical tweezers it is possible to exert torques to twist or rotate microscopic objects. Both spin and orbital angular momentum can be transferred. This transfer can be achieved using birefringent particles exposed to a Gaussian circularly polarized beam. In this case, a transfer of spin angular momentum will occur. The change in spin, and hence the torque, can be readily measured optically. On the other hand, it is much more challenging to measure orbital angular momentum and torque. Laguerre-Gauss mode decomposition, as used for orbital angular momentum encoding for quantum communication, and rotational frequency shift can be used, and are effective methods in a macro-environment. However, the situation becomes more complicated when a measurement is done on microscale, especially with highly focused laser beams. We review the methods for the measurement of the angular momentum of light in optical tweezers, and the challenges faced when measuring orbital angular momentum. We also demonstrate one possible simple method for a quantitative measurement of the orbital angular momentum in optical tweezers.

Paper Details

Date Published: 16 February 2011
PDF: 13 pages
Proc. SPIE 7950, Complex Light and Optical Forces V, 79500I (16 February 2011); doi: 10.1117/12.886221
Show Author Affiliations
Halina Rubinsztein-Dunlop, The Univ. of Queensland (Australia)
Theodor Asavei, The Univ. of Queensland (Australia)
Daryl Preece, The Univ. of Queensland (Australia)
Alexander B. Stilgoe, The Univ. of Queensland (Australia)
Norman R. Heckenberg, The Univ. of Queensland (Australia)
Timo A. Nieminen, The Univ. of Queensland (Australia)

Published in SPIE Proceedings Vol. 7950:
Complex Light and Optical Forces V
David L. Andrews; Enrique J. Galvez; Jesper Glückstad, Editor(s)

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