Abstract

We describe a means for controlling the spin angular-momentum flux of a laser beam at constant power, without introducing any elliptical or linear polarization. This allows a controllable torque, acting to spin the particle uniformly, to be exerted on a birefringent particle in optical tweezers. The constant power means that transverse and axial trapping, and heating due to absorption, are unaffected by changing the torque. The torque can be computer controlled and rapidly changed. In addition, the lateral trapping is kept constant. Very low torques can be obtained such that rotational Brownian motion of birefringent particles can be observed. This has the potential to greatly extend the quantitative applications of the rotation of birefringent objects in optical tweezers.

© 2009 Optical Society of America

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History
Original Manuscript: October 14, 2008
Revised Manuscript: November 12, 2008
Manuscript Accepted: November 24, 2008
Published: January 12, 2009

References

Author Affiliations

Maren Funk, Simon J. Parkin, Alexander B. Stilgoe, Timo A. Nieminen, Norman R. Heckenberg, Halina Rubinsztein-Dunlop

The University of Queensland

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